Bio 530 Module 5

prostate problems

Benign Prostatic Hypertrophy Mucosal glands and stroma proliferate Stimulated by dihydrotestosterone Results in narrowing of the prostatic urethra causing difficult urination and retention of urine by the bladder Cancer of the prostate Most common cancer in males affecting 1 in 20 males 70% of males between 70 -80 yrs will get it Develops in the main glands Detected by a combination of blood level of PSA and rectal examination Benign Prostatic Hypertrophy is an abnormal proliferation of stromal and epithelial cells in the mucosal region that crowds the urethra. The theory as to how this happens is autocrine stimulation of stroma cells and paracrine stimulation of epithelial cells by dihydrotestosterone leads to too much proliferation of stroma and epithelial cells that occurs commonly in the mucosal glands. The prostatic urethra lumen becomes too small so urination becomes difficult and the bladder retains urine. Cancer of the prostate develops most often in the main glands of the prostate. 70% of males between 70-80 yrs old will develop prostatic cancer. Detection of cancer relies on rectal palpation of the prostate feeling for bumps on the surface of the gland where the main glands are located combined with determining whether the blood level of PSA is elevated.

Uterine Tube Functions

Capture, nutrition and transport of ovulated oocyte Transport and Capacitation of sperm Site of fertilization - distal third Unless fertilized, oocyte remains viable for about 24 hours Zygote, the fertilized oocyte, takes about 5 days to arrive in uterus The uterine tubes capture the oocyte, and provide nutrition for it as it travels through the tube. The uterine tubes provide a pathway for sperm to be transported and the secretions of the uterine tube mucosal cells weakens the cell membrane of the sperm over the acrosome giving it the capacity to release enzymes to break through the zona pellucida to fertilize an ovum. This is called capacitation of the sperm. The uterine tube also is the site where normally fertilization takes place. An oocyte can remain viable for about 24 hours in the uterine tube before it dies. If the ovum is fertilized it is now called a zygote and it takes about 5 days for the zygote to arrive in the uterus.

chemically hormones

Amino acids: :Thyroid- thyroid hormone :Adrenal medulla- epinephrine and norepinephrine Peptides: :pituitary gland-oxytocin and antidiuretic hormone Proteins: :Pancreas-insulin & glucagon :Pituitary-prolactin Steroids: :testis-testosterone, ovary-estrogen and adrenal cortex-corticosterone Their chemical nature can be either amino acids, secreted by the thyroid gland and adrenal medulla cells, peptides, secreted by the pituitary gland, proteins, secreted by the pancreas and pituitary, or steroids secreted by the testis, ovary and adrenal cortex.

in the non pregnant human female the granular tissue of breast consist of

ducts only

which region of the retina is responsible for the sharpest vision

fovea centralis

tight junctions between which of the following cells make up the blood-retina barrier

retinal pigmented epithelial cells

which cell is responsible for the blood-testis barrier

sertoi cell

which cell plays a key role in removing excess cytoplasm from a spermatid

sertoli cell

which is the final step in the perception of sound just prior to the generation of actin potential (nerve impulse) in the cochlear nerve that will transmit sound information to the auditory cortex of the brain

shear forces between tectorial and basilar membranes

the fallopian tube oviduct is lined with what kind of epithelium

simple columnar

which is the next stage of spermatocytogenesis

spermatid

epididymus

1.Epididymis A. Head B. Body C. Tail Single highly coiled tube 4 - 6 meters in length The epididymis is a coiled tubule 4-6 meters long in which the sperm emerge and enter the ductus deferens with forward motility. In other words something happens in the epididymis to activate the flagellum of each sperm. Androgen binding protein in the epididymis brings about a concentration of testosterone in the lumen of the epididymis higher than that in the blood.

wat is the chromosome number in the cells in the adluminal compartment of the seminiferous tubule epithelium

1n

Thyroid Activity States

Hyperthyroid and hypothyroid activity states are compared to normal in the three panels in this slide. In the left panel observe that the hyperthyroid state is associated with smaller follicles having less stored colloid indicating that the thyroid follicular cells are in a state of greater activity in synthesizing and releasing hormone - note that the cells are cuboid with some columnar. In the right panel you can observe the hypothyroid state is associated with larger follicles full of colloid (stored hormone) and lower cuboidal or flattened follicular cells. In the middle panel the normal state is illustrated - larger follicles than the hyper state, but smaller follicles than the hypo state. In the normal thyroid not all follicles are as illustrated here. You could expect to find some with more and some with less activity, but the overall state would be normal.

Rete Testis

In this trichrome stained specimen you can see that the mediastinum is composed of a significant amount of collagen that serves as a supporting connective tissue for the thin walled and delicate network of tubules called the rete testis.

pancreas endocrine and exocrine

Islets are usually oval shaped and stain lighter than the surrounding exocrine gland cells. Their size ranges from 0.1 - 0.2 mm (100 - 200 microns) in diameter. Note how the islet has a very close relationship with the surrounding exocrine acini

Leydig Cells source of testosterone

Leydig Cells Leydig cell structure - acidophilic cytoplasm - rounded nucleus - smooth ER -mitochondria with tubular shaped cristae LH dependent Secretion of Leydig cells (full name: Interstitial cells of Leydig) reside in the tissue between the seminiferous tubules. Because the tubules are round there is ample space for this collection of cells. Considering that there can be up to 1200 seminiferous tubules the interstitial tissue is considerable. Leydig cells have organelles that are typical of cells that synthesize steroids - smooth endoplasmic reticulum and special mitochondria with tubular shaped cristae. Under the influence and stimulation of LH (luteinizing hormone from the anterior pituitary) Leydig cells synthesize and secrete testosterone. Testosterone diffuses from the Leydig cells into the interstitium gaining entrance to blood vessels and to the cells of the seminiferous tubules, and, also to the lumen of the seminiferous tubules. The androgen binding protein secreted by sertoli cells helps the testosterone bind to the developing sperm cells and sperm.

Hypothalamus - Pituitary

Location Just below and attached to the hypothalamus by a stalk, the infundibulum Surrounded and protected by bone Lies in a saddle- shaped depression of the sphenoid bone, the 'sella turcica' (a Turkish Saddle Size Pea-sized Weight Males - 0.5 gm Females - 0.5 gm Multiparous females 1.5 gm Now the histology and function of the pituitary and pineal gland will be presented. Note the close relationship between the pituitary gland and the hypothalamus. This will be important to recall later in this lecture. The pituitary gland lies just below the hypothalamus and is connected to the hypothalamus by a stalk called the infundibulum. The pituitary is surrounded and protected by bone because it lies in a depression of the sphenoid bone shaped like a Turkish Saddle, anatomically referred to as the 'sella turcica'. The pituitary gland is about the size of a pea weighing about 0.5 gm in males and 1.5 gm in multiparous women (given birth two or more times).

Milk Synthesis and Secretion

MFG = milk fat globule CLD = cytoplasmic lipid droplet ME = myoepithelial cell FDA = fat depleted adipocyte PC = plasma cell Figure 4, page 259 in Clinics in Perinatology: Clinical Aspects of Human Milk and Lactation - Eds. Carol L. Wagner, MD & Dilip M. Purohit, MD, Vol. 26, Number 2, June 1999 I. Exocytosis of milk protein, lactose, and other components of aqueous phase in Golgi derived vesicles II. Milk fat secretion by way of the Milk Fat Globule III. Direct movement of monovalent ions, water, and glucose across the apical membrane IV. Transcytosis of components of the interstitial space V. The paracellular pathway for plasma components and leukocytes Milk protein, lactose and other water soluble components of milk are synthesized in rough endoplasmic reticulum and the Golgi apparatus. Milk fat secretion is accomplished by a portion of the cell membrane being pinched off (apocrine secretion). Ions, water and glucose move across the apical membrane. Secretory IgA from plasma cells in the interstitium are moved to the lumen of the secretory alveolus by transcytosis (movement through the cell). Some components of plasma and leukocytes, lymphocytes and neutrophils, move between the secretory cells into the lumen.

epididymus

Surrounded by smooth muscle cells which move sperm by peristalsis As pointed out in the next slide, the cilia in the epididymis are stereocilia. They are non-motile. Forward motion by the sperm is by the whipping of their tails (middle, principal and end piece). Smooth muscle cells surrounding the epithelium facilitate this forward movement of sperm.

The Internal Ear

Two labyrinthine compartments bony labyrinth (blue) semicircular canals vestibule cochlea membranous labyrinth (pink) vestibular labyrinth semicircular ducts utricle saccule cochlear labyrinth cochlear duct The inner or internal ear consists of two labyrinths. One is composed of bone called the bony labyrinth that forms the semicircular canals, the vestibule and the cochlea. The membranous labyrinth is contained within the bony labyrinth. The membranous labyrinth is composed of two divisions: the vestibular and the cochlear labyrinths. The vestibular membranous labyrinth has three components - semicircular ducts lying with the semicircular canals, a utricle (labeled U) and a saccule (labeled S). The cochlear membranous labyrinth contains the cochlear duct. There are three spaces related to the bony and membranous labyrinth that contain fluid of different ionic strengths. The next slide will present these spaces and their contents.

Pars Distalis: Connective Tissue

Trichrome Stain-Stroma stained blue Cross-section through a cord of parenchymal cells, Here, in this specimen of the adenohypophysis stained with a trichrome stain, you can see the blue stained connective tissue and can observe how the connective tissue encloses groups of cells. One of the groups is indicated. This is a cross-section through a cord of pars distalis cells that includes the three types -acidophils (a), basophils (b) and chromophobes (c) - one of each is labeled.

Tubuli Recti and Rete Testis

Tubuli recti and rete testis are located in the mediastinum of the testis.

Ovulation and Corpus Luteum

When ovulation occurs, the follicle collapses and at first there is bleeding from capillaries of the theca interna into the antrum that produces a clot. Then, cells of the granulosa (now called granulosa lutein cells) and of the theca interna (now called theca lutein cells) proliferate rapidly forming the corpus luteum. The cells of the corpus luteum secrete progesterone and estrogens that simulate the maturation and secretory activity of the endometrium so that the endometrium is prepared to receive a fertilized ovum for implantation and then pregnancy. If a fertilized egg implants into the uterus endometrium, then eventually, the placenta will maintain the corpus luteum. If not, 10 - 12 days after ovulation the corpus luteum degenerates leaving a scar composed of connective tissue. The scar is called a corpus albicans.

pineal gland

5-8mm The pineal gland is a small pea-like protrusion from the posterior wall of the third ventricle in the region of the midbrain. It is noteworthy for three reasons. It has been long thought of as the third eye, one that can peer into the metaphysical and spiritual realm. It produces melatonin, a hormone involved in the sleep- wake cycle with some influence on reproductive readiness. The cell which produces melatonin is called the pinealocyte. With age calcified spheres accumulate that are called brain sand. It is a convenient landmark for radiological examination and interpretation of brain films. This image illustrates brain sand in a histological preparation stained with H&E. The brain sand (alias acervuli or corpus arenaceum) is basophilic.

hormones

biologic substance acting on specific target cells They are secreted into the interstitium, find their way into the bloodstream and act upon certain other cells in the body.

Thyroid Hormones Synthesis - Storage - Release

Calcitonin lowers blood calcium levels •Thyroxine - T4 •(tetraiodothyronine) •Triiodothyronine - T3 •Regulates metabolism, heat production, and influences body growth & development This slide shows three thyroid follicular cells and one parafollicular cell (C-cell). Observe that the parafollicular cell is within the basement membrane of the follicle intimately related to the follicular cells but it is smaller, does not border the surface of the colloid and secretes its product, calcitonin, directly into the fenestrated with diaphragms capillaries surrounding the follicle. Calcitonin lowers the calcium level in blood by reducing calcium absorption in the small intestine, by suppressing the bone resorptive activity of osteoclasts, and by promoting calcium deposition in bones through the stimulation of osteocytes to move calcium into bone matrix and formation of more bone by osteoblasts. Observe the relationship of the follicular cells to the colloid (storage form of thyroid hormone) and the fenestrated capillaries. The follicular cells synthesize two hormones, thyroxine (T4) and triiodothyronine (T3). These hormones regulate metabolism of body cells, promote heat production by influencing the uncoupling of mitochondria energy production so heat is generated in cells, and influences body growth and development. Observe that the follicular cell takes in tyrosine and iodine from the blood, and then synthesizes a complex of the thyroxine (T4) and triiodothyronine (T3) with a globular protein resulting in the colloid within the follicle. This thyroglobulin is secreted by exocytosis into the follicle and now is the stored form of thyroid hormone. The thyroid gland is the only endocrine gland that stores its hormone in the gland outside of the cells that produced it. When more thyroid hormone is needed in the blood, the follicular cell takes in thyroglobulin by endocytosis, then by action of enzymes in lysosomes in a special intracellular compartment - the endosome- the two hormones are separated from the globular protein and secreted into the fenestrated capillaries at the base of the cell. This entire process is under the influence of thyroid stimulating hormone (TSH) from the anterior pituitary.

Hypo- & Hyperthyroidism

Diseases of the thyroid gland result in it either being hyperfunctionalorhypofunctional. Anexampleof hypothyroidism is when one of the essential ingredients, iodine, is lacking or deficient in the diet. This causes an abnormal amount of stored hormone resulting in a goiter. There is insufficient levels of thyroid hormone circulating that causes the pituitary to ramp up its release of TSH that induces the thyroid gland to produce more and more stored hormone, but, due to the fact the there is no iodine or it is deficient, the hormone is ineffective. Thus the gland enlarges. The term for an enlarged thyroid gland is: goiter. Observe the histology consisting of very large follicles linen by squamous cells because the thyroid gland is storing its entire defective hormone in the colloid. In contrast one of the conditions of hyperthyroidism is Grave's disease that has visible signs of an enlarged thyroid (a goiter) and protruding eyeballs (exophthalmos). Graves' disease S l i d e 1 4 S l i d e 1 5 is a condition where plasma cells influenced by sensitized T-cells produce Thyroid Stimulating Immunoglobulins which compete for and bind to the TSH receptors of follicle cells resulting in an over active thyroid gland. The feedback on the pituitary to reduce TSH does not work because the TSI's keep on being produced. Observe the histology consisting of small follicles lined by cuboidal to columnar cells and the interface between the follicular cells and the colloid is very scalloped indicating a high level of thyroid hormone secretion. Symptoms include weight loss, excessive sweating, tachycardia and nervousness. Hypothyroidismistreatedbyprescribing exogenous thyroid hormone (now synthesized) and hyperthyroidism is treated by either surgically removing the thyroid gland or radiotherapy by ingestion of radioactive iodine that destroys most active follicular cells.

Mammary Gland Proliferating Lobules During Pregnancy

During pregnancy, the influence of estrogen causes cells making up ducts and secretory units to proliferate resulting in more ducts and an impressive expansionofsecretoryunits. Progesteronecauses the secretory cells to mature and to begin synthesizing and secreting milk.

a thyroid follicle is a solid mass of cuboidal cells

false

enlargement of the main glands of the prostate gland may result in difficult urination and retention of urine in the urinary bladder

false

glial cells in the pineal gland synthesize and secrete melatonin

false

parathormone is secreted by the oxyphil cell located in the parathyroid gland

false

spermatocytogenesis is the process of forming a spermatogonium cell from a stem cell

false

the cell in an islet of langerhans that secretes a hormone that lowers glucose level in blood is the alpha cell

false

the cell in the thyroid gland that secretes calcitonin is called the thyroid follicular cell

false

the cornea has prism shaped fibers that contain collagen type IV

false

the ear ossicles are located in the internal ear compartment

false

the hyaloid canal runs from the optic nerve to the cornea through the vitreous body

false

the limbus of the eye is where the ciliary body merges with the choroid

false

the main difference between endocrine and exocrine glands is whether or not their ducts branch

false

the seminiferous tubules converge at the tunica albuginea of the testis

false

at which stage of folliculogen does an antrum first appear

secondary

choose all that contain endolymph

semicircular duct, scala media

select all that are true in regard to the type of epithelium that may be found lining thyroid follicles in different functional states of the thyroid gland

simple columnar, simple squamous, simple cuboidal

chose all that are components of the middle ear

stapes, tensor tympani muscle, malleus, stapedius muscle, auditory tube, incus

the perikaryon of the cells that secrete oxytocin are located in which of the following sites

supra optic and paraventricular nuclei of the hypothalamus

where are the cells located that produce testosterone

testis- interstitium

Female External Genitalia

Collectively known as the vulva the female external genitalia are: Mons pubis - a rounded prominence over the pubic symphysis, formed by subcutaneous adipose tissue Labia majora - two large longitudinal folds of skin, homologous to the skin of the scrotum containing a thin layer of smooth muscle resembling that of the dartos muscle of the scrotum Labia minora - paired, hairless folds of skin that border the vestibule (entrance to the vagina) and are homologous to the skin of the penis Clitoris- erectile structure homologous to the penis contains two small erectile bodies, the corpora cavernosa and the glans clitoris. The skin over the glans is very thin and contains numerous sensory endings. Vestibule - entrance way to the vagina is lined with stratified squamous non- keratinizing epithelium with mucus glands that open near the opening of the vagina.

the middle ear

Components tympanic cavity, auditory tube, auditory ossicles. The middle ear consists of the tympanic cavity, the auditory ossicles and the auditory tube (Eustachian tube). The tympanic membrane separates the external acoustic meatus (ear canal) from the middle ear. The tympanic membrane has three layers from outside to inside and they are: 1) skin of the ear canal, 2) radially and circularly arranged collagen fibers and 3) a mucous membrane that also lines the entire tympanic cavity. The tympanic membrane is similar to a drum. The ear ossicles connect the tympanic membrane to the oval window of the cochlea (colored green). The cochlea and vestibular apparatus are inner ear structures. The ossicles are constructed of bone. The bones of the middle ear convert sound waves to mechanical vibrations in fluid filled chambers inside the cochlea. The malleus (like a hammer) is attached to the tympanic membrane. The stapes (shaped like a stirrup) has a foot plate that fits into the oval window of the cochlea. The incus (like an anvil) links the malleus to the stapes. Two muscles attach to the ossicles and affect their movement. The tensor tympanic muscle lies in a bony canal above the auditory tube and its tendon inserts on the malleus. Contraction of this muscle increases tension on the tympanic membrane (analogous to tuning a drum). The other is the stapedius muscle that lies in a bony eminence on the posterior wall of the middle ear. Its tendon inserts on the stapes. Contraction of this muscle dampens the movement of the stapes at the oval window. The stapedius muscle is only a few millimeters long, the smallest skeletal muscle in the body. Thus the tympanic membrane reverberates with sound waves. The reverberations are picked up by the manubrium of the malleus and transmitted through the incus to the stapes that transmits the reverberations to the ovalwindowofthecochlea. Theauditorytube (Eustachian tube) is around 3.5 cm long. It is lined with ciliated pseudostratified columnar epithelium similar to respiratory epithelium. It is normally collapsed but opens during yawning and swallowing. The auditory tube equalizes pressure of the middle ear with atmospheric pressure.

Ear 3 Chambered Sensory Organ

External ear: Auricle (pinna, external auditory meatus, & tympanic membrane (eardrum) Middle ear: air-filled space (tympanic cavity) in temporal bone, containing malleus (hammer), stapes (stirrup) and incus (anvil) Internal ear: a bony and membranous labyrinth The ear is the anatomical organ that functions as an auditory system for sound perception and as a vestibular system for balance. The ear is made up of three parts that are termed external, middle and internal. The external ear collects sound waves. It includes the pinna (also called auricle), the ear canal (external auditory meatus), and the superficial layer of the ear drum (also called the tympanic membrane). The middle ear converts sound waves to vibrations. It is an air-filled cavity behind the ear drum (tympanic membrane) that includes three ear bones or ossicles: the malleus (or hammer), incus (or anvil), and stapes (or stirrup). The Eustachian tube is also a part of the middle ear. The Eustachian tube has an opening into and communicates with the pharynx. The internal ear functions are balance and the conversion of vibrations created from sound waves in the middle ear to nerve impulses. It includes the semicircular canals for balance and the cochlea for hearing.

function of pineal gland

Function is via secretion of melatonin that inhibits gonadotropin induces sleepiness Melatonin secretion by pineal gland is: increased by darkness decreased by light Melatonin is sold over the counter to promote going to sleep hasten recovery from jet lag The pineal gland is a photosensitive organ and an important time keeper and regulator of the day/night cycle (the circadian rhythm). It obtains information about light and dark cycles from the retina of the eye via of a nerve pathway from the retina to the hypothalamus to the pineal gland via the suprachiasmatic nucleus (a collection of neurons that lie just above the site where the optic nerves from either eye cross). During the day light impulses inhibit the production of melatonin, conversely, melatonin production is increased during darkness. This is important in humans in regulating daily body rhythms. In animals it has been shown that melatonin decreases the production of releasing factors from the hypothalamus that stimulate the release from the piutitary of follicle stimulating hormone and luteinizing hormone, both of which are important for ovulation. Thus, darkness is associated with decreased sexual activity in animals. Length of day has influence on animal sexual behavior. Shine a light into a female rabbits eyes and it will ovulate. Recent studies in humans suggest that the pineal gland has a role in sudden changes in day length, such as those experienced by travelers who suffer from jet lag. Melatonin is sold over the counter. It is advertised for jet lag to take one tablet of melatonin when you arrive at your destination each day for the length of days equal to the number of hours your daily rhythm has changed. It is also suggested as a sleep aid. Short term use seems to be safe as to aid in recovering from jet lag. Effects of regular daily long term use have not been determined.

adrenal glands

Gross Structure paired, retroperitoneal glands two parts cortex and medulla thick connective tissue capsule innervated by sympathetic nerves Adrenal glands are classified as solid organs with a cortex and medulla. Adrenal glands are paired, one on either side located just superior to the kidneys. They are retroperitoneal, meaning they lie behind or posterior to the peritoneum lining the posterior wall oftheabdominalcavity. Theglandsgrosslycanbe seen to consist of two parts, the cortex that encloses a medulla. Blood vessels enter the cortex and leave via the medulla. The adrenal gland is innervated by sympathetic nerves that are especially important in the medulla.

histosection of the adrenal gland

Stroma: has a distinct capsule but there is little connective tissue stroma in the gland which has a very rich blood supply and the capillaries are sinusoidal Parenchyma: Cells of three types in cortex and two types in medulla Blood supply: dual arrangement Some arterioles to cortex then to medulla by cortical sinusoids which carry corticosteroids Other arterioles directly to medulla for high O2 The adrenal cortex is yellowish and accounts for 80 - 90% of the gland. The adrenal medulla is reddish in color and accounts for 10 - 20% of the gland. Note that the cortex occupies a greater portion of the gland than the medulla. One the next slide we will see a magnification of the boxed in area.

Eye Layers & Chambers

Layers Corneoscleral coat (fibrous) cornea & sclera Vascular (Uvea) choroid, ciliary body, iris Retina Pigmented & neural Chambers Anterior Posterior Vitreous This image is an anterior-posterior histological section through the middle of an eye stained with hematoxylin & eosin. Note first that I stands for iris and AC stands for anterior chamber. Observe the three layers and the three chambers. The outermost layer is the called the coreoscleral layer (also called the fibrous layer). The composition of the cornea and sclera is dominated by collagen fibers, yet the sclera, the white of the eye, is opaque while the cornea is transparent. The cornea transparency is due to the fact that the collagen fibers are orthogonally arranged and the water content of the cornea is kept low. The vascular layer (Uvea) is composed of the choroid (containing blood vessels), the ciliary body and the iris. The vessels of the choroid nourish the retina. The ciliary body and iris are anterior extensions of the choroid. The ciliary body contains smooth muscle cells that via of zonula fibers that extend from it to the lens allow the eye to accommodate (the lens power is modified). The iris also contains smooth muscle that operates to make the pupil (hole) smaller or larger to change the light exposure to the retina. The retina has two layers, the pigmented epithelium and the neural containing the photoreceptors. The neural retina is thicker at the posterior 1/3 of the eye globe because that is where the photoreceptors and layers of neurons are located. So the eye globe has three layers and three chambers. The rest of this lecture will focus on the histology and function of these components of the eye.

Posterior Lobe:Pars Nervosa

Neuron Cell Bodies in hypothalamic nuclei project axons to capillary beds in pars nervosa synthesize hormones, ADH and oxytocin hormones complexed to carrier protein, neurophysin, accumulate in Herring bodies along the axons Special cells named pituicytes (a type of neuroglial cell) surround and support the axons The pars nervosa differs from the pars distalis. Neuron cell bodies in the hypothalamus synthesize two hormones that are bound for the pars nervosa. Axonal processes of these neurons whose cell bodies are located in the hypothalamus carry two hormones, ADH and Oxytocin, from the hypothalamus to the posterior pituitary where, upon appropriate stimulation, the hormones are released from the nerve terminals into the capillaries present. Special cells called pituicytes surround and support the delicate axons when they reach the pars nervosa.

Accommodation (lens change to focus objects)

Normal resting state ciliary muscle relaxed zonula fibers are taut /tensed lens pulled into a thin shape short focal length Near object brought to the eye contraction of ciliary muscle zonula fibers become slack lens becomes thicker focal length shortens light rays converge image on retina Accommodation is the process by which the elastic & flexible lens becomes rounder to focus the image of a nearby object on the retina and flatten when a distant object is focused. The ciliary muscle, the ciliary body and the zonula fibers (forming the lens suspensory ligament) contribute to the process of accommodation. When the ciliary muscle relaxes the zonula fibers are taut or tensed so that the lens is pulled into a thin shape enabling distance vision, the normal resting state of the eye (emmetropia from the greek meaning - in proper measure). When the ciliary muscle contracts the ciliary body moves closer to the lens thereby making the zonula fibers slack that results in the lens becoming thicker toward a spherical shape thus focusing the light rays of a closer object onto the retina. Looking at close objects like reading a book or focusing on a computer screen is work requiring energy because the ciliary smooth muscles cells must remain in a contracted state. This is the reason our eyes become tired. When reading or working on the computer, or, other activities requiring focusing on nearby objects it is a good idea to rest the eyes frequently by looking at a distant object. The drawing on the right illustrates two common conditions that are changes from normal. If the eyeball shape from anterior to posterior is two deep (long) or the curvature of the lens is not flat enough, the image of distant object forms in a plane in front of the retina and is not in focus, but close object are in focus. This is called nearsightedness (myopia). Eyeglasses with concave shaped lenses are provided to change the focal length so that the light rays are focused on the retina. If the eyeball shape from anterior to posterior is too shallow and the curvature of the lens is too flat, the distant object is formed at a plane behind the retina. Distant objects are in focus but close objects are not. This is called farsightedness (hyperopia). To correct this condition eyeglasses with convex lenses are prescribed.

optic nerve

Optic Nerve begins at optic papilla/disc 400,000 myelinated axons originate in Retina ganglion cells Carries information from photoreceptor cells Rods Cones Axons terminate in brain Visual cortex optic papilla (retinal area 1.5 mm in diameter lacking retina neurons) optic nerve The optic nerve originates at the posterior pole of the eye at a place called the optic papilla. It is disc shaped and cupped in the center. Optic cup and optic papilla are referring to the center and the rim, respectively. The optic papilla is really a part of the retina but does not contain any retina photoreceptor cells, only the axons coming from the retinal ganglion cells. This is the site where all of the axons from those ganglion cells converge and then leave the eye forming the optic nerve. There are on the order of 400,000 axons that are collected in the optic nerve. They travel in this nerve until the optic chiasma a place where the optic nerves cross and then the journey is by the right and left optic tracts until the axons terminate in the visual cortex so that information collected by the retinal photoreceptor cells is converted into images. The last part of the eye we will learn about is the structure that makes it possible to see objects in sharp focus.

Sensory Cells Membranous Labyrinth

Sensoryhaircellsinsixsensory regions Three cristae ampullari Ampullla of 3 semicircular canals Two macula One in the utricle & one in the saccule One in spiral organ of Corti In the cochlear duct Sensoryhaircellsare Mechanoelectric transducers stereocilia in auditory system true cilia in the vestibular system Electrical signals produced in Organ of corti by Movement of stereocilia Vestibular apparatus by Movement of stereocilia in reference to kinocilia (true cilia) There are six regions of the membranous labyrinth where sensory hair cells are located. They are mechanoelectricaltransducers. Theyconvert movement into electrical signals (nerve impulses). The drawing upper right shows the locations of these sensory cells (patches colored green). Three are located in the ampullae of the semicircular canals. They are called cristae ampullari (singular- crista ampullaris). Two are macula or flat shaped and they are located, one in the utricle and one in the saccule. The sixth one follows the contour of the spiral organ of Corti. The schematic drawing of a hair cell below illustrates the true cilia and stereocilia that are in the vestibular system. The auditory system hair cells in the organ of Corti do not have cilia. Mechanical movement of the stereocilia in reference to the cilia of hair cells in the vestibular system is converted into neural impulses that sense our position in space. Mechanical movement of the sterocilia in the auditory system is converted into sound. Each hair cell is synaptically connected to nerve endings at its base. This is a complex electrophysiological process that cannot be present in more detail here.

histology of pineal gland

Stroma: surrounded by a capsule that is continuous with the pia/arachnoid meninges, gland is attached to dorsal aspect of diencephalon and 3rd ventricle via stalk Parenchyma: two cell types Pinealocyte: large basophilic cells with processes ending near capillaries, pinealocytes are connected via gap junctions, produce serotonin and melatonin Glial (interstitial) cells: resemble astrocytes and play a supportive role for pinealocytes The pineal gland is surrounded by a capsule that is continuous with the pia/arachnoid meninges. It attached to the dorsal aspect of the diencephalon and the 3rd ventricle via stalk. The parenchyma of this gland consists of pinealocytes that secrete the hormone melatonin and some serotonin. Glial cells are also present and play a supportive role for pinealocytes.

summary

This lecture began by defining and distinguishing between endocrine and exocrine glands / organs followed by a presentation of endocrine, paracrine and autocrine secretory methods. Next hormones were defined as chemical substances secreted by cells that act upon other cells, or, in some cases upon the same cell that secreted the substance. The endocrine glands and where they are distributed in the body was presented. Next, the pituitary gland was presented explaining and illustrating the cells and the hormones of the anterior and posterior pituitary. The close relationship between the hypothalamus and the pituitary was emphasized, including the hypothalamo-hypophyseal portal system and its significance. Finally, the histology of pineal gland was presented explaining that its secretion is melatonin by the pinealocytes.

summary

This lecture began with a presentation of the visible parts of the eye and proceeded to an explanation and location of the three layers and chambers of the eye. Next the lens of the eye was illustrated and it relationship to the zonula fibers and ciliary body was explained. The production, circulation and drainage of aqueous humor was presented. The histological structure of the neural and pigmented retina was illustrated and described followed by the optic disc, optic nerve and blood vessels. Emphasis was placed on the photoreceptors, rods and cones, and the role they play in black/white and color vision. Then, the macula, fovea and fovea centralis was presented with emphasis on the structure and function of the fovea centralis as it relates to sharp vision. Finally, how the eye works to accommodate for close up objects was illustrated and explained.

summary

This lecture began with an overview of the female reproductive organs, namely, the ovaries, uterine tubes, uterus, cervix, vagina and the mammary glands. The ovary was presented next that included a detailed illustration of the parts of the ovary the stages of how an oocyte develops in follicles in the cortex of the ovary. Ovarian follicular development was related to hormone changes. The uterine tubes were presented next emphasizing their role in transport of the ovum and facilitation of movement of sperm to the point of fertilization in the distal third of the uterine tube. Following that the uterus was presented along with the phases of the endometrium correlated with the menstrual cycle and blood levels of estrogen and progesterone. Vagina histology was presented next. The lecture concluded with a presentation of the mammary gland histology prior to puberty, at puberty, during pregnancy and the nursing mother.

summary

This lecture began with an overview of the male reproductive organs showing the relationship between the testis, epididymis, ductus deferens, prostatic urethra and the penile urethra. The accessory glands were displayed and how they relate to the ductus deferens and prostatic urethra. Next the histology of the testis was presented explaining the exocrine function - secretion of sperm and the endocrine function -secretion of testosterone. The seminal vesicle histology was presented in detail along with the three phases of spermatogenesis - spermatogonia phase, spermatocyte phase and the spermitid phase (spermiogenisis). The various ducts that lead out of the testis and the ductus deferens were illustrated and described. Finally, the accessory sex glands - the prostate, the seminal vesicles and the bulbourethral glands were presented. The lecture concluded with a presentation of the histology of the penis that included an explanation of the mechanism of erection.

summary

Thislecturebeganwithanoverviewofthethreeearcompartments-the external, middle and internal ear. Thecomponentsoftheexternalear,thepinnaandexternalauditorymeatus were described and illustrated next. Then,thecomponentsofthemiddleear,thetympaniccavity,theauditory ossicles and auditory tube were presented, illustrated and described. Followingthat,thecomponentsoftheinternalear,thelabyrinthine compartments, the sensory cells, the vestibular apparatus, the cochlea and the organ of Corti were illustrated and described. Thenthewayinwhichthevestibularapparatussensesandtranducesinto electrical signals angular movement, acceleration and deceleration movement and gravity was explained. Finallythewayinwhichtheauditoryapparatussensesandtransduces sound waves into electrical signals was explained.

summary

Thislecturebeganwiththehistologyofthethyroidglandinwhichthethyroid follicle and its colloid were illustrated and described. Thethyroidfollicularcellwasthenpresentedwithillustrationsofitshistology followed by an explanation of its function. Thethyroidfollicularcellandtheparafollicularcell(C-cell)werecomparedasto histology and location and the function of the C-cell was explained. Anexplanationandillustrationofhyperthyroidismandhypothyroidismwas presented next. Thenthehistologyandfunctionoftheparathyroidglandwaspresented. Theadrenalglandswerethenillustratedshowingthedifferencebetweenthe cortex having three zones and the medulla along with the cells and their secretion. Thespecialhistologyandfunctionoftheadrenalmedullachromaffincellwas presented. Finally,theendocrineportionofthepancreas,theisletsofLangerhanswas presented with primary emphasis on the insulin and glucagon cells.

Contents Labyrinthine Compartments

Three fluid filled spaces Endolymphatic space within membranous labyrinth Return to outline Endolymph within semicircular ducts, ampulla, scala media of cochlea Similar to intracelluar fluid, high in potassium, low in sodium Perilymphatic space between bony wall and membranous labyrinth Perilymph within semicircular canals surrounding semicircular ducts, utricle and saccule. Also present within the scala vestibuli and scala tympanic of the cochlea. Similar in composition to extracellular fluid, low potassium, high sodium Cortilymphatic space within the organ of Corti Cortilymph in the organ of Corti True intercellular space with fluid similar to extracellular fluid There are three distinctly different spaces within the labyrinthine compartments. The space within the membranous labyrinth contains endolymph, a fluid similar to intracellular fluid. Endolymph is within the semicircular ducts, ampulla, utricle, saccule and the scala media of the cochlea. The space between the bony wall of the bony labyrinth and the wall of the membranous labyrinth contained within is filled with perilymph, a fluid similar to extracellular fluid. Perilymph is in the space surrounding the semicircular ducts, utricle, and saccule. It is also present within the scala vestibuli and the scala tympani of the cochlea. The corticolymphatic space is an intercellular space that lies within the organ of Corti. It contains cortilymph that has a composition similar to extracellular fluid.

Intratesticular Ducts

1. Tubuli Recti (Straight Tubules) 2. Rete Testis (in Mediastinum Testis) 3. Ductuli Efferentes (Efferent Ductules) Now the story in this lecture shifts from the formation of sperm to the transportation of sperm from the testis to the outside. The ducts illustrated in this slide are still within the testis. The tubuli recti are short straight tubules that carry the sperm from the open ends of the seminiferous tubules to the rete testis in the mediastinum, which is a network of tubules that provide a collecting area. From this network of tubules multiple short ducts provide a connection between the rete testis and the epididymis. These are called the efferent ductules.

aqueous humor

Aqueous humor is similar to plasma in its concentration of ions like sodium, chloride, calcium etc, but it has only 0.1% protein compared to 7% in plasma. The capillaries in the ciliary processes are fenestrated so that tissue fluid is readily available to the columnar epithelial cells covering the ciliary body that secrete the aqueous humor. Aqueous humor circulates in the posterior and anterior chambers of the eye and bathes the vitreous body as well. This enlargement of one of the ciliary processes shows a two layer columnar epithelium covering the process containing blood vessels. The epithelium next to the process connective tissue core is pigmented and the epithelium covering the process is not pigmented. The cells of the non-pigmented covering epithelium sit on a basal lamina that borders the posterior chamber. The apical pole of these cells faces inward so that they take in the fluid and secrete it through the basal compartment through the basal lamina into the posterior chamber. Aqueous humor is collected by special vessels in the limbus region (point at which the cornea meets the sclera). The enlargement of this area shows the trabecular spaces that are at the junction of the iris with the sclera into which the fluid flows from the anterior chamber. From there the fluid is emptied into the canal of Schlemm, a canal that extends circumferentially around the eye at the limbus. The canal of Schlemm communicates with veins on the surface of the sclera. From that point on the fluid is carried away into the blood. If there is excessive secretion aqueous humor or the outflow via the canal of Schlemm is blocked or constricted, pressure in the eye will increase because the layers of the eye will not expand to accommodate the increased pressure. The average value of intraocular pressure is 15.5 mmHg with fluctuations of about 2.75 mmHg. Intraocular pressure varies throughout the night and day. The diurnal variation for normal eyes is between 3 and 6 mm Hg and the variation may increase in glaucomatous eyes. During the night, intraocular pressure usually decreases due to the slower production of aqueous humor. Intraocular pressure also varies with a number of other factors such as heart rate, respiration, exercise, fluid intake, systemic medication and topical drugs. Alcohol consumption leads to a transient decrease in intraocular pressure and caffeine may increase intraocular pressure. Raised intraocular pressure above 21 mmHg is a significant risk factor for damage to the retina and the optic nerve, a condition known as glaucoma. One person may develop nerve damage at a relatively low pressure, while another person may have high eye pressure for years and yet never develop damage. Untreated glaucoma leads to permanent damage of the optic nerve and resultant visual field loss, which can progress to blindness. A thorough eye exam by an optometrist or ophthalmologist always includes measuring intraocular pressure with a tonometer.

Follicular Atresia

As previously stated normally, only one follicle matures to the stage of ovulation. Several begin dropping out at various times from the primary, secondary to the beginning stage of becoming a graafian follicle. The image on the left contains a follicle that is just at the beginning of forming an antrum and a follicle to the right of it that is regressing. The right image shows such a follicle at higher magnification. Follicles that are regressing or degenerating are resolved mostly by apoptosis of the follicle cells and the oocyte but often some tissue remains as a slight scar.

Ovarian Follicle Theca Interna & Externa

As the follicle enlarges and matures the follicular granulosa cells are proliferating. Stromal cells that immediately surround the follicle also proliferate resulting in the formation of a connective tissue sheath. Eventually, the sheath develops in an outer part that is mainly smooth muscle cells, fibroblasts and collagen fibers, and an inner part that is composed of secretory cells surrounded by capillaries so it has a rich blood supply. The enlargement of the rectangular area in this graafian follicle contains the sheath and some of the follicle lumen containing granulosa cells. The two layers are clearly seen on either side of the dotted line. The inner part of the sheath is the theca interna and the outer part is the theca externa. Observe the thin pink staining basal lamina between the follicle and the theca interna. The theca interna are composed of granulosa cells (forming the stratum granulosum) that differentiate into cells that secrete androgen precursors to estrogen. These androgen precursors diffuse into the follicle and the precursor is transformed into estrogen that then diffuses out of the follicle to enter the blood capillaries in the theca interna. The estrogen target is twofold - the stimulation of mitosis of endometrial gland cells and the growth of ducts and alveolar secretory cells of the breast. The theca interna cells are under the influence of LH (luteinizing hormone).

Ovarian Follicles Primordial, Primary, Multilaminar Primary

At birth the cortex of the ovary is the home of around 400,000 immature oocytes surrounded by one layer of flat cells and a basal lamina. This histological arrangement is called a primordial follicle. Each primordial follicle contains an oocyte that is arrested in the first meiotic division and will remain that way until puberty. At this stage the oocyte is called a primaryoocyte. AtpubertywhenFSH(follicle stimulating hormone) levels reach a critical level in the blood the primary oocyte increases in size and the squamous follicle cells become cuboidal and then columnar producing a unilaminar primary follicle. As time passes during the menstrual cycle the primary oocyte increases in size further and the follicle cells begin to proliferate producing a primary follicle with multiple layers of follicle cells - the multilaminar primary follicle. The multiple layers of follicle cells are called the stratum granulosum. At this stage another structure appears - the zona pellucida. The growing oocyte secretes this structure that is composed of glycosaminoglycans and glycoproteins. It stains pink with eosin and is PAS positive. At ovulation the zona pellucida stays with the oocyte. After fertilization of an oocyte by a spermatozoon, the zona pellucida is dissolved, a process known as hatching after which development of the embryo begins. The zona pellucida has a role in fertilization, sperm binding, preventing polyspermy, blastocyst development and preventing premature implantation (ectopic pregnancy). The zona pellucida is commonly used to control wildlife population problems by immunocontraception. When the zona pellucida of one animal species is injected into the bloodstream of another, it results in sterility of the second species due to immune response. This effect can be temporary or permanent, depending on the method used. In New Jersey, Porcine zona pellucida is used to keep deer populations low, and this process is commonly referred to as "spay-vac".

Cervix: External Os

At the external os, the opening from the cervical canal into the vagina, a sudden transition from simple columnar epithelium lining the cervical canal to stratified squamous non-keratinizing epithelium occurs. In the right image, an enlargement of the transition, you can observe that this is very abrupt. In sites like this where epithelial types change abruptly, there is a greater possibility for cancer to develop. Monitoring of this epithelium by a physician who makes a smear of this epithelium, a PAP SMEAR, is important to pick up any changes that may lead to cancer.

Histology of Pars Distalis

Cells present are of two types Chromophils: cells that are stainable Acidophils somatotrophs secrete growth hormone lactotrophs secrete prolactin Basophils thyrotrophs secrete thyroid stimulating hormone corticotrophs secrete ACTH gonadotrophs secrete FSH and LH Chromophobes: cells that do not stain are degranulated acidophils and basophils The pars distalis contains two main cell types; they are chromophils and chromophobes. Chromophils are cells that are stainable and they are of two types - acidophils that secrete growth hormone and cells that secrete prolactin, a hormone that facilitates female breast milk production, and basophils that secrete thyroid stimulating hormone, adrenal cortex stimulating hormone and gonad stimulating hormones. Chromophobes are cells that are not stainable and are thought to be degranulated acidophils and basophils.

adrenal cortex

Compare the left panel, a histological section through the entire cortex of an adrenal gland and a portion of the medulla. Observe the three zones - the glomerulosa, the fasciculata and the reticularis. The glomerulosa, overall more basophilic than the other zones, is composed of cell clusters resembling the glomeruli of the kidney. The zona fasciculata has columns of cells containing steroids that stain lighter due to the lipid content. The zona reticularis is a network of cells that take up more cytoplasmic stain. Two main products are produced by the adrenal cortex - mineral corticoids (aldosterone) and glucocorticoids (corticosterone). Aldosterone is secreted by the zona glomerulosa cells. It acts on the distal tubules of the nephron in the kidney, the gastric mucosa, salivary glands and sweat glands to stimulate resorption of sodium. The zona glomerulosa is under the feedback control of the renin-angiotensin-aldosterone system. Renin is released in the kidney due to low blood pressure. Renin converts angiotensinogen to angiotensin I which is converted to angiotensin II in the lung. Angiotensin II stimulates zona glomerulosa cells to secrete aldosterone that raises the level of sodium in the blood and hence blood volume is increased resulting in an increase of blood pressure. When blood pressure is returned to normal, renin release in the kidney is inhibited. The zona fasciculata is under the influence of ACTH (adrenal cortex trophic hormone) that comes from the anterior pituitary. Increased ACTH increases the synthesis and release of glucocorticoids by zona fasciculata cells. In general glucocorticoids regulate glucose synthesis and the polymerization of glycogen, the stored form of glucose, mainly found in the liver. Glucocorticoids also depress the immune system and the inflammatory response. Physicians may prescribe steroids to combat inflammation. Ibuprofen and aleve are over the counter non-steroidal anti-inflammatory agents that have similar results. The zona reticularis has a very minor role secreting some glucocorticoids and sex hormones. Some evidence suggest these cells are worn out zona fasciculata cells and thus are dying. It is thought zona fasciculata cells are renewed by stem cells just under the capsule. The medulla has two cell types- autonomic ganglion neurons and chromaffin cells that synthesize and secrete norepinephrine and epinephrine.

prostatic glands distribution

Composed of 30 - 50 branched tubuloalveolar glands whose ducts empty into the prostatic urethra The glands of the prostate are distributed in three concentric layers: an inner mucosal layer, an intermediate submucosal layer, and a peripheral layer containing the main prostatic glands. The glands of the mucosal layer secrete directly into the urethra. The glands of the other two layers have ducts that open into the prostatic sinuses located on either side of the urethral crest on the posterior wall of the urethra.

penis erection mechanism

Erection of the penis is caused by increased penis blood flow resulting from the relaxation of the tunica media of penile arteries and corpus cavernosum smooth musculature. This response is mediated by the release of nitric oxide (NO) from the pudendal nerve & endothelial cells, which stimulates the synthesis of cGMP in smooth muscle cells. Cyclic GMP causes the sequestration of Ca++ thereby inducing muscle relaxation which causes greater in- flow. The anatomical relationship of arteries to veins also helps as the expanded relaxed arteries compress the veins thereby decreasing outflow. The inhibition of phosphodiesterase type 5 (PDE5) enhances erectile function by increasing the amount of cGMP. Drugs like Viagra, Cialis and Levitra (all trademarked) inhibit PDE5, thus enhancing erectile function.

mammary glands

Female Breast at Puberty -estrogen dependent -growth of lactiferous duct -adipose tissue -collagenous CT -but alveoli remain small Breasts during pregnancy -estrogen, progesterone, prolactin, and human placental lactogen dependent -mainly growth and maturation of secretory components, i.e. the cells of the alveoli Males and Females have mammary glands. In development potential multiple glands can develop along a 'mammary line'. Many animals have multiple glands bilaterally. In humans, two breasts (mammary glands usually referred to as breasts in humans) are located on either side overlying the pectoral muscles of the thorax. This is a drawing of a female lactating breast as it would look inside during the later stages of pregnancy. Breasts are modified apocrine sweat glands. They consist of ducts and glandular units enclosed in connective tissue and adipose tissue. The secretory units are called tubuloalveolar units and they are organized in lobules with ducts draining the lobules. The lobules drain into a few long straight ducts, the lactiferous ducts that empty into the lactiferous sinus that opens to the outside at the nipple. In males little additional development occurs normally in postnatal life - the glands remain rudimentary. In females the breasts undergo further development under hormonal influence. They are also influenced by changes in ovarian hormone levels during each menstrual cycle.

Sharp Vision Fovea Centralis

First a brief explanation of how the lens is supplied with nutrients. Observe the hyaloid canal in the drawing of a section through the eye globe. The hyaloid canal is a small transparent canal running through the vitreous body from the optical nerve disc to the lens. The canal has two functions. One is that it provides a low viscous pathway for flow of fluid to nourish the lens. The other is to compensate for lens thickness changes when we focus our eyes. It provides an adjustable reservoir of mobile liquid which may be easily and rapidly displaced backwards in positive accommodation, forwards in negative accommodation. The upper right image is what an ophthalmologist sees during examination of the eye using an ophthalmoscope. Note the optic disc and how the blood vessels spread out from it. A circular area of about 5.5 mm in diameter to one side of the optic disc is the macula lutea. It is yellowish due to the presence of a pigment called xanthophyll. In the center of the macula lutea is the fovea centralis. The diameter of the fovea centralis is 0.2 - 1.0 mm. The term fovea means pit. Observe the histological section and the drawing of the fovea centralis below the ophthalmoscope photo where you can see that the retina is reduced to only two layers, a layer of cones and the pigmented epithelium. This is the area the produces sharp vision. Retinal vessels are absent in this region. The retina here gets its blood supply from the vessels in the choroid, which is across the retinal pigment epithelium and Bruch's membrane. The high spatial density of cones accounts for the high visual acuity capability at the fovea. This is enhanced by the local absence of retinal blood vessels from the fovea, which, if present, would interfere with the passage of light striking the foveal cone mosaic. Approximately 50% of the nerve fibers in the optic nerve carry information from the fovea centralis, while the other 50% carry information from the rest of the retina. The fovea centralis comprises less than 1% of retinal size but takes up over 50% of the visual cortex in the brain. Compared to the rest of the retina, the cones in the foveal centralis have a smaller diameter and can, therefore, be more densely packed (in a hexagonal pattern). The macula lutea that contains the fovea centralis is the region of the eye subject to dry and wet macular degeneration, a condition, where the accumulation of excess tissue fluid (edema) or debri interferes with sharp vision. If edema, it is called wet macular degeneration. If debri accumulates, it is called dry macular degeneration.

Seminal Vesicle Mucosa

Folded mucosa with pseudostratified columnar epithelium Secretes -fructose -citrate -inositol -prostaglandins Contributes 70% of ejaculate Stimulated by testosterone The mucosa of the seminal vesicle is highly folded. The epithelium lining the lumen is pseudostratified columnar epithelium. The secretion of the seminal vesicle is a whitish yellow and viscous material. It contains fructose, the principal metabolic substrate for sperm. Citrate, inositol and prostaglandins are also secreted by these glands. Nearly 70% of the volume of the ejaculate comes from the seminal vesicles. The gland is maintained and stimulated by testosterone. Contraction of the smooth muscle of the wall of the seminal vesicles during ejaculation discharges the secretion of these glands into the ejaculatory ducts and helps to flush sperm out of the urethra.

Ovarian Follicles Secondary and Graafian

Follicle development continues under the stimulation of FSH and progresses to a structure called the secondary follicle. The follicle still contains a primary oocyte arrested in the diplotene stage of the first meiotic division. The follicle cells increase in number so that there are as many as 12 layers to the stratum granulosum. The follicle cells secrete a hyaluronan rich fluid that pushes the cells apart forming a cavity called the antrum (A). As the follicle continues to develop still under the influence of FSH, the secretion of the follicle cells caused the antrum to enlarge and compress the granulosa cells around the perimeter while the oocyte is surrounded by a layer of cells called the corona radiata. The oocyte now sits on a pedestal of cells called the cumulus oophorus. The stromal cells, granulosa cells forming the stratum granulosum, immediately surrounding the follicle are induced to transform into cells that will eventually secrete an estrogen precursor molecule. This layer of stromal cells is now called the theca interna. At this stage the follicle is mature and is named Graafian follicle (synonym is tertiary follicle).

Seminal Vesicles General Structure

Highly tortuous ~ 15 cm long tube Epithelial lined tube with wall of smooth muscle The seminal vesicles are paired glands. They are elongated glands with a highly folded mucosa. A short excretory duct from each seminal vesicle combines with the ampulla of the ductus deferens to form the ejaculatory duct.

neurohypophysis

Hypothalamus Neurohypophysis infundibulum & pars nervosa Return to outline Hypothalamic Nuclei secrete oxytocin and vasopressin Supraoptic Nuclei (collection of neurons) Paraventricular Nuclei (collection of neurons) Neurosecretory neurons producing oxytocin & vasopressin/ADH Hormones travel down the axons bound to the carrier protein - neurophysin Oxytocin and vasopressin are stored in expansions of the axons called Herring bodies until they are released after cleavage from neurophysin Inferior arteries * Capillaries into which the hormones are secreted The neurohypophysis produces two hormones. Oxytocin and vasopressin (ADH) are produced in cell bodies of at least 3,000 neurons located in two sites in the hypothalamus. One population of neurons is located in the supraoptic nucleus (SO) and the other in the paraventricular nucleus (PV). Recall that a collection of neuron cell bodies in the CNS is called a nucleus whereas a collection of neuron cell bodies outside of the central nervous system is called a ganglion. The axons of the neurons in these two nuclei extend to the pars nervosa via the infundibular stem. The hormones synthesized in the cells bodies of these neurons travel through the axons to axon terminations in the pars nervosa. In the pars nervosa unique expansions along the axons called Herring bodies store the hormones. The release of these hormones into the vasculature occurs in the pars nervosa. Observe the drawing noting that arteries enter the pars nervosa, the blood passes through capillaries picking up the hormones and then blood leaves through the veins so the hormones are delivered via the blood to the target organs / cells.

pars distilas electron microscropy

Illustration of storage granules in pars distalis Secretory cells. Secretory cells store their hormones in granules. Granules are of different sizes so it is possible to make estimated identification based on granule shape and size, but no conclusive identification of hormone stored by routine EM or LM. This electron micrograph of cells in the pars distalis is included to illustrate that the acidophils and basophils store their secretory products in secretory granules and release their products regulated by the action of releasing factors from the hypothalamus. These cells secrete by the regulatory method as compared to the constitutive method. Regulatory methods means the product is stored in the secretory granules and released periodically when stimulated to do so. Constitutive secretion means that the product is not stored but released continuously as in a plasma cell releasing antibody.

Ectopic Pregnancy in the Fallopian Tube

In cases of abnormal nidation (normal nidation is the process by which an embryo burrows into the endometrium of the uterus -also known as implantation- nidation is from the Latin term nidus which means nest), in which the embryo implants itself in the tube (ectopic pregnancy), the lamina propria reacts like the endometrium of the uterus, forming numerous decidual cells. Because of its small diameter, the oviduct cannot contain these new cells and bursts, causing extensive hemorrhage that can be fatal if not treated immediately.

Anterior Pituitary Cells & Hormones

In the anterior pituitary, mainly in the pars distalis there are two types of acidophils and three types of basophils. One type of acidophil is called a mammotroph and it produces prolactin, a milk stimulator to facilitate milk production in the pregnant female. The other type of acidophil is called a somatotroph, a hormone that facilitates growth, the growth hormone. The three types of basophils are gonadotrophs, thyrotrophs and corticotrophs. Gonadotrophs produce both luteinizing hormone (a hormone that facilitates ovulation and the formation of and maintaining of the corpus luteum in the ovary during pregnancy) and follicle stimulating hormone that stimulates the maturation of eggs in the ovary prior to ovulation. Thyrotrophs produce one hormone, the thyroid-stimulating hormone that causes the thyroid to synthesize and release more thyroid hormone into the blood. Corticotrophs produce one hormone, the adrenocorticotrophic hormone that stimulates mainly the zona fasciculata in the adrenal cortex to produce and release more cortico-steroids.

parathyroid HandE stain

In this higher magnification view of the parathyroid gland, observe that the nuclei of chief cells appear more viable, i.e., euchromatic, whereas the nuclei of the oxyphil cells appear less viable and heterochromatic. Note the intimate association of the capillaries with erythrocytes with the chief cells. Oxyphil cells have no known function. The rather intense eosinophilic staining of the oxyphil cell cytoplasm is due to the fact that these cells are jam packed with mitochondria. Again, no known function. Oxyphil cells have been found to increase with age.

Pituitary Tumor: adenoma

Normally in a view of the pars distalis like this acidophils and basophils can be seen. This tumor has only one cell type, the acidophil -specifically the somatotroph. Too many somatotrophs > too much growth hormone > overgrowth of bones of face and hands > Acromegaly Adenoma is a benign epithelial neoplasm (new growth) producing a gland pattern, or derived from gland cells. All of the cells in this microscopic field of a specimen of the adenohypophysis of the pituitary are acidophils due to the neoplastic growth (abnormal proliferation) of somatotrophs (acidophils) resulting in a tumor called an adenoma (adenoma because the cells of origin of the tumor are gland cells). This is a tumor of the pituitary that occurs in adults. Somatotrophs produce growth hormone. The excessive somatotrophs in this tumor result in abnormally high blood levels of growth hormone. Since the epiphyseal plates are closed bones cannot grow any more in length. Bones get wider and thicker due to appositional growth. The skull, arms and hands, especially become heavy and thick as illustrated in this drawing of a person withanadenomaofpituitaryacidophils. The condition is called acromegaly (acro - top and megaly - large, literally means the top part of the body is enlarged or thicker. A look at the person's hands would be as this image shows. So this is a pituitary adenoma

pancreas endocrine and exocrine

Note that the exocrine gland cells are arranged in acini. The Islet cells are arranged in cords. Observe in the histological section that blood vessels (fenestrated capillaries) are in close relationship with the cells. The cells within the islets are 4 types: beta cells are the majority and they secrete insulin, alpha cells are next in number and they secrete glucagon. Delta cells (D cells) are less in number and they secrete somatostatin. PP cells are least in number and they secrete pancreatic polypeptide. Insulin facilitates the uptake and storage of glucose. Inadequate levels of insulin as in diabetes lead to elevated levels of glucose in the blood. Insulin has multiple functions that mainly result in the utilization of glucose. Glucagon has the opposite effect. It stimulates the release of glucose into the blood stream. Somatostatin has properties similar to somatotropin the hypothalamus factor that stimulates release of growth hormone. Somatostatin's role coming from the pancreas is not clear. It has been shown to inhibit the action of both insulin and glucagon. PP cells are a minor component. There product pancreatic polypeptide that stimulates gastric chief cells, inhibits bile secretion and intestinal motility.

adrenal blood vessels

Note the two pathways of blood flow to the medulla from the cortex. One is directly via arterioles to the medulla and the other is via capillaries throughout the cortex. The direct flow via arterioles to the medulla supplies the medullary cells with oxygen. The other pathway provides a means to deliver trophic hormones like ACTH to the cells of the cortex, and to pick up products of the cortex cells like cortisol.

Eye: 3 Layers & 3 Chambers

Now we turn to the histology of the eye globe. First observe the eye has two poles, an anterior and a posterior. The lens is located anteriorly and the optic nerve emerges at the posterior pole. The fibrous layer consists of the sclera that is opaque and the cornea that is transparent. The vascular layer consists of the choroid, the ciliary body and the iris. The retinal layer consists of a pigmented part and a neural part - where the photoreceptors (rods and cones) are located. The anterior chamber is the space between the cornea and the iris. The posterior chamber is the space between the iris and the lens. Both of these chambers contain a watery fluid that nourishes the cornea and lens. The vitreous chamber is the space between the posterior surface of the lens and the neural retina. This chamber contains a gelatin like mass, the vitreous body that contains a fluid called the vitreous humor. The vitreous body acts as a shock absorber to protect the delicate neural retina and to keep it in place.

Seminiferous Tubule: Histological Section

Now you are viewing a portion of a round seminiferous tubule at a magnification sufficient to see the details of the cell types of which it is composed. At the bottom of the image is the tunica fibrosa. From this region to the lumen the stages in the development of a sperm can be seen. It is mixture of supporting cells (Sertoli cells) and spermatogenic cells. Spermatogonia are stem cells. Sertoli cells enclose and support spermatocytes and spermatids as they transform into sperm. Note that the primary spermatocytes are in mitosis - prophase (preserved in this stage when the specimen was fixed). Staging of the spermatocytogenic cells is done by nuclear appearance as you will see in the next few slides.

Menstrual Stages of Endometrium

Observe in each of the images of specimens of the endometrium that there is a functional layer adjacent to the lumen of the uterus and a basal layer near the myometrium. The functional layer goes through a 28 day cycle. The basal layer is constant. It contains reserve stem cells that restore the functional layer after menstruation. The cycle begins with ischemia, death and sloughing of the functional part of the endometrium due to the fact that pregnancy did not occur and therefore both the source of estrogen and progesterone from the corpus luteum was shut down. A sudden drop in estrogen causes the arteries supplying blood to the endometrium to constrict. This phase lasts about 5 days. The proliferative stage lasts about 9 days during which time the endometrial glands are growing in length under the influence of estrogen. Later in this stage progesterone coming from the granulosa follicle cells and eventually the corpus luteum has its effect, which is to influence the maturation of the gland cells for their secretory function. This leads to the secretory stage that lasts about 14 days where the glands become saw-toothed shaped because the epithelium has grown so much that it folds. The gland cells are now columnar and begin secreting a product rich in glycogen to nourish development if implantation of the conceptus occurs. If an ovum is not fertilized, then the two hormone levels fall off sharply resulting in constricted arteries that cause ischemia and hypoxia of the endometrium. The functional part of the endometrium becomes necrotic and sloughs off with some bleeding. This is the menstrual stage that lasts up to 5 days and so the cycle begins anew.

Seminiferous Tubules

Observe several profiles of seminiferous tubules. The outer boundary of one is indicated by the lines. Look inside them and see that there are many round basophilic structures. These are the nuclei of cells in different stages of sperm development (spermatogenesis). The sperm forming cells are stratified, that is, in layers. They are embraced by special epithelial cells, the Sertoli cells. Each tubule is enclosed within (or you could say, wrapped by) layers of connective tissue named tunica fibrosa. Also, note that there is tissue between the tubules. Within this interstitial tissue area some very important cells that produce testosterone are housed, namely, Interstitial Cells of Leydig. The next slide shows a portion of a seminiferous tubule at higher magnification as indicated by the boxed-in area.

rods and cones

Observe that the layer of rods and cones is almost the deepest layer of the retina - the pigmented epithelial layer is the only one deeper. Light must pass through all of the layers of neurons, supporting cells and nerve processes before it interacts with the photoreceptors. The retina contains approximately 120 million rods and 7 million cones. The rods are about 2 micrometers thick and range from 40 to 60 micrometers long. They contain a pigment, rhodopsin, in the membranous sac of the rod outer segment. The cones vary in length from 85 micrometers at the fovea (the small area to one side of the optic cup responsible for sharp vision) to 25 micrometers at the periphery of the retina. Cones contain a different pigment, iodopsin. It is the interaction of light with these pigments that starts the process of converting light into neural (electrical) impulses. The rods are the most sensitive to light so they are responsible for vision in conditions of low light. The rod pigments have maximum absorption at 496 nm on the visual spectrum so that the image formed is composed of gray tones (black and white). Vitamin A levels are critical to normal function of these cells. Persons with vitamin A deficiency have difficulty seeing in dim light. There are three types of cones L, M and S. Long (L), middle (M), and short (S) wavelength sensitive. They are less sensitive to low light but more sensitive to red, green and blue of the visual spectrum. Cones provide a visual image composed of color by mixing the appropriate proportion of red, green and blue light. Almost 90% of the human population can mix a given color from impulses generated in all three classes of cones and they are known as trichromats. True color-blind individuals (almost all are male) are dichromats and are believed to have a defect in either the red-, green- or (much less commonly) blue- sensitive cones. There are two major types of color blindness: those who have difficulty distinguishing between red and green, and those who have difficulty distinguishing between blue and yellow. The condition is hereditary. Color blindness is usually classed as a mild disability, but in certain situations, color blind individuals have an advantage over those with normal color vision. There are some studies which conclude that color blind individuals are better at penetrating certain color camouflages. Color blindness, either partial or total, is commonly caused by a birth defect in the cones. Total color blindness can be caused by trauma to the visual centers of the brain due to some injury.

retina

On the left is a histological section of the retina that almost matches the labeled drawing on the right. The retina has ten layers containing 15 types of neurons and 38 different types of synapses. You are not expected to know all of the layers. You should learn that there are four groups of neurons and supporting cells. They are 1) photoreceptors - rods and cones, 2) conducting neurons - bipolar and ganglion cells, 3) association neurons, and 4) supporting neuroglial cells. The optic nerve fiber layer is next to the vitreous body. The retinal pigment cells in the pigment epithelium, the outer most layer of the retina, perform two important functions. First, they absorb light passing through the neural retina preventing light from reflecting off the choroid that reduces glare. Second, the epithelial cells in this layer are connected with the junctional complex composed of tight junctions, adhering junctions and gap junctions. They are physically bound together tightly. They can communicate with one another via the gap junctions. The tight junctions between the cells constitute the main component of the blood-retina barrier that isolates the retinal cells from blood borne substances that could be harmful such as bacteria. Indeed, the retina is an amazing complex arrangement of nerve cells, nerve fibers and supporting cells. This presentation only touches the surface of retinal histology and physiology.

Graafian Follicle & Ovulation

Ovulation is the process in which a secondary oocyte arrested in metaphase of the second meiotic division is released from the Graafian follicle. In humans the norm is that one follicle undergoes ovulation. There can be several, but usually only one. The follicle destined to ovulate in any menstrual cycle is recruited from several primary follicles in the first few days of the cycle. During ovulation the oocyte surrounded by the corona radiata cells erupts through the follicular wall including the germinal epithelium. In the image on the right the white mass just emerging from the ovary is the secondary follicle surrounded the corona radiata. The end of the Fallopian tube (uterine tube) is trumpet shaped with a large surface area covered with ciliated cells. The ovum is swept up by the uterine tube and begins it journey toward the uterus. If it is fertilized by a sperm, the second meiotic division is completed. Pause this presentation to view the videos illustrating ovulation.

paracrine

Paracrine is a process whereby a cell secretes a chemical that acts on nearby cells, e.g. the mast cell secreting histamine that acts on nearby endothelial cells. e.g. Mast cell secretes histamine which acts on nearby endothelial cells

Parafollicular cells

Parafollicular or C cells can be distinguished from the thyroid hormone secreting follicular cells by the lack of cytoplasmic staining. Immunostaining with antibodies against calcitonin make it possible to identify the cells with certainty as illustrated here. The thyroid gland actually, then, produces two hormones -thyroid hormone and calcitonin. Thyroid hormone is stored in the follicle as thyroglobulin (hormone bound to a globular protein) but calcitonin (also referred to as thyrocalcitonin) is not stored. It is secreted via the interstitium into the capillaries.

thyroid and parathyroid histology

Parathyroid glands are located within the thyroid gland. Parathyroid glands share the thyroid gland capsule. Note the contrasting histology patterns of thyroid and parathyroid. The cells of the parathyroid gland are organized into cords (strands) of cells compared to the spherical epithelial lined follicles of the thyroid gland.

Pineal Gland: H&E Stain

Pinealocytes is what arrow is pointing to These cells make and secrete melatonin Secretion follows a 24 hour rhythm Maximum secretion is a night Promotes rhythmic changes in secretory activity of gonads A pinealocyte in indicated in this specimen of a pineal gland. These cells secrete mainly melatonin and the secretion follows a 24 hour rhythm. The maximum secretion is at night or whenever the body is in the dark.

Prostate Gland Epithelium

Psuedostratified columnar Produces prostatic fluid which contributes to the ejaculate. Fluid contains amino acids citric acids and enzymes, especially alkaline and acid phosphatase PSA = Prostate Specific Antigen This is a closer look at one prostatic glandular alveolus containing a concretion and the epithelium that lines the alveolus. The combined secretions of the seminal vesicles and the prostate gland make up the seminal fluid. When sperm is added to this fluid the proper term is semen. The average ejaculate of semen has a volume of about 3 ml and normally contains up to 100 million sperm per ml. It is estimated that 20% of the sperm in any ejaculate are morphologically abnormal and nearly 25% are immotile.

epididymus epithelium

Psuedostratified columnar epithelium with stereo cilia The epithelium of the epididymis is pseudostratified columnar epithelium with stereocilia. The stereocilia are not motile. They project into the lumen and are thought to increase the surface contact of the epithelium with sperm to facilitate sperm maturation.

endocrine gland

Secretions into blood vessel or sometimes to the same cell or its neighbor ENDOCRINE Glands without ducts Endocrine gland capillaries are of the discontinuous type that have fenestrations with diaphragms Endocrine glands have no ducts. The hormones produced by endocrine glands are secreted directly into the interstitium. The hormone enters into the blood circulation in capillaries that have fenestrations, making it easy for the hormone to be picked up and delivered to a distance site to its target organ / cell.

exocrine gland

Secretions into lumen of gastrointestinal tract or body surface EXOCRINE: Glands with ducts Exocrine glands secrete their products into ducts which lead directly into the lumen of the gastrointestinal tract or onto the body surface. They are the counterparts to endocrine glands (pituitary, thyroid, parathyroid, adrenal and the islets of Langerhans in the pancreas) that do not have ducts and secrete their products (hormones) directly into the bloodstream or release hormones into the interstitium that affect neighboring target cells nearby the release site. Exocrine glands have ducts.

Uterine Tube Mucosa

Secretory cells -nutrition for ovum -capacitation for sperm The mucosal lining of the uterine tubes is simple columnar epithelium of two types - one is ciliated, called ciliated cells and the other type is non-ciliated that secrete nutritive substances for the ovum, called the peg cell. The epithelium has a mixture of these cells as this specimen illustrates. The epithelial cells undergo cyclic hypertrophy during the follicular phase of ovarian follicle development and atrophy during the luteal phase after ovulation. The ratio of ciliated cells to nonciliated cells changes. Estrogen stimulates ciliogenesis and progesterone increases the number of secretory cells. At about the time of ovulation the epithelial cells grow to a height of nearly 30 micrometers and then shrink to half that height just before the onset of menstruation.

rete testis

Simple cuboidal epithelium supported by a connective tissue substrata The rete testis is a complex series of interconnecting channels (a network) within the highly vascularized connective tissue of the mediastinum. A simple cuboidal epithelium lines the network of channels. The cells have a single apical cilium and some also apically located microvilli.

Pars Distalis: Immunostain

Specific subtypes of pars distalis cells may be demonstrated by immunostaining For example: somatotroph is made visible by antibody to growth hormone. Acidophils somatotroph mammotroph Growth hormone Prolactin arrows in the image are pointing to somatotrophs This specimen of the pars distalis was subjected to an immunocytochemical method with antibodies specific against growth hormone. Therefore, one can be assured that the brownish stained cells contain growth hormone. This is the only means whereby one can separate a somatotroph from a mammotroph both of which react as acidophils when stained with H&E.

Phases of Spermatogenesis

Spermatogenesis begins with the spermatogonia phase during which spermatogonia divide to provide a population of cells that are committed to becoming sperm. While they are dividing they are interconnected but eventually a type B spermatogonia emerges and these are the committed cells. During the next phase, spermatocyte phase, type B spermatogonia undergo DNA replication to produce a primary spermatocyte that has twice the normal number of chromosomes so they have 4n chromosomes and twice the amount of DNA as spermatogonia. Each chromosome is duplicated but held together with a centromere resulting in connected chromatids. This makes the primary spermatocyte have the equivalent of 4 times the amount of DNA as normal cells. Then, still in this spermatocyte phase two divisions occur. The first is a reductional division (the first meiotic division) that results in a cell called the secondary spermatocyte that has 1n chromosomes and 2 times DNA. Then the primary spermatocytes divide by mitosis during which time the centromeres dissolve and the chromatids separate and distribute into four spermatids which are haploid, 1n. The next phase is the spermatid phase also known as spermiogenesis where the spermatids undergo a remodeling of their cytoplasm and nuclear shape while generating a flagellum and thus forming sperm.

Spermatid Phase: spermiogenesis

Spermiogenesis is the process whereby a spermatid is transformed into a spermatozoon (plural-spermatozoa). First note at the lower right the location of anterior and posterior of the spermatid maturing into a spermatozoon. The phases are Golgi, Cap, Acrosome and Maturation. The Golgi phase main event is that glycoprotein and enzyme containing granules are being formed in the Golgi apparatus. These granules are collected into a membrane bound vesicle called the acrosomal vesicle. The centrioles migrate behind the nucleus to prepare to generate the microtubules that will form the flagellum of the sperm. The cap phase event is that the acrosomal vesicle spreads over the anterior half of the nucleus and the nuclear contents begin to condense becoming more and more heterochromatic. In the acrosome phase the events are that the sperm becomes deeply embedded in the Sertoli cell at its head points toward the basal lamina. The developing flagellum extends into the lumen of the seminiferous tubule. The condensed nucleus of the spermatid flattens and elongates, the nucleus and acrosome move to a position adjacent to the anterior plasma membrane, and the cytoplasm is displaced posteriorly. The cytoplasmic microtubules organize into a cylindrical sheath called the manchette that extends from the posterior pole of the spermatid. The last phase is the maturation phase in which excess cytoplasm in the residual bodies is phagocytized by the Sertoli cell. The attachment between the spermatids is lost so the mature sperm is now released from the Sertoli Cell ready to enter the lumen of the seminiferous tubule. The acrosome now contains hyaluronidase, neuraminidase, acid phosphatase and a protease. These enzymes will be released to help the sperm gain entrance to the oocyte through the zona pellucida. The mature sperm (spermatozoon) is around 60 micrometers long with the head containing the male chromosomes measuring 4.5 micrometers long, 3 micrometers wide and 1 micrometer thick. About 300 million sperm are produced daily in the human testis.

Sertoli Cells: Structure & Function

Support of interconnected developing cells Phagocytosis of excess spermatid cytoplasm shed as residual bodies Secretion of -fluid for sperm transport -androgen-binding-protein which is FSH dependent -Inhibin which suppresses FSH Form the blood-testis barrier by being connected to each other by tight junctions Sertoli cells are large cells with moderately eosinophilic cytoplasm and oval nuclei that usually display a nucleolus. They are the epithelial lining of the seminiferous tubules. If all developing sperm cells were removed they would be seen to form a simple columnar type lining of the tubule. Sertoli cells embrace and surrounding the cells of the three phases of spermatogenesis (gamete development) - spermatogonial phase, spermatocyte phase and the spermatid phase. Sertoli cells support the cells involved in these phases. They phagocytose excess cytoplasm as spermatids are transforming into spermatozoa. They secrete fluid for sperm transport and androgen binding protein that helps testosterone from Leydig cells to stay in the tubule to interact with the developing cells and sperm. The synthesis and secretion of androgen binding protein by the Sertoli cell is stimulated by Follicle Stimulating Hormone (FSH) from the anterior pituitary gland. Sertoli cells form a barrier between the blood and the developing sperm cells, the blood-testis barrier. SERTOLI CELLS ARE POST-MITOTIC - THEY DO NOT DIVIDE.

adrenal medulla

The adrenal medulla is responsible for producing and infusing adrenalin (epinephrine) into the blood vascular system. Observe the large veins in the medulla, the largest of which is the central medulla vein. These veins have smooth muscle in their wall that can propel the blood out of the adrenal medulla into the vena cava rapidly - the mechanism giving us a "shot of adrenalin". If the boxed in area of the low magnification view on the left is enlarged we see the chromaffin cells, the main cells of the medulla (the name is derived from the observation that these cells take up potassium dichromate which renders them brown in the so-called 'chromaffin reaction'. They are seen in the enlarged view as clusters of cells close to small blood vessels. They are in intimate contact with fenestrated with diaphragms capillaries. If the boxed in area of the magnified view is examined in more detail the relationship between the chromaffin cells and their innervation and proximity to fenestrated capillaries can be seen as illustrated this drawing. Chromaffin cells synthesize and secrete epinephrine and norepinephrine. However the final product that enters the veins of the medulla is epinephrine (adrenalin) because norepinephrine is converted to epinephrine by a converting enzyme that is activated by gluocorticoids from the cortex. The sudden release of adrenalin from the medulla establishes conditions for maximum use of energy and thus maximum physical effort. This energy comes from breakdown of glycogen releasing large amounts of glucose into the bloodstream, increase in blood pressure by direct action of epinephrine on smooth muscle of arterioles, dilation of coronary vessels to increase blood flow to heart muscle, dilation of blood vessels in skeletal muscle, increase in heart rate and blood pumped with each heart beat, constriction of blood flow to skin and the gastrointestinal tract and an increase in the rate and depth of breathing. For brief periods of time, in an extremely stressful situation, persons have been reported to lift objects way beyond that possible normally.

pituitary gland divisions (hypophysis)

The anatomical parts of the pituitary gland and its intimate relationship with the hypothalamus are shown on this slide. Observe that the anterior lobe has two distinct parts - the pars distalis and the pars tuberalis. Both parts are derived embryologically from oral ectoderm. There is also a region called the pars intermedia, mostly consisting of epithelial lined cysts that are remnants from development. The pars intermedia is also from oral ectoderm. Observe that the posterior lobe has two parts - the pars nervosa and the infundibulum. Both parts of the posterior lobe are derived embryologically from neuroectoderm. The infundibulum is a continuation of the hypothalamus so that the posterior pituitary is really an extension of the hypothalamus of the brain. During development the oral ectoderm came from an evagination of oral ectoderm that enveloped the down growth of the developing brain.

external ear

The auricle (pinna)- visible ear component External auditory meatus (ear canal) - canal leading to middle ear The external ear consists of the auricle (also called the pinna) and the ear canal (also called the external auditory meatus). The auricle is the oval appendage that projects from the lateral surface of the head. A small projection at the bottom is called the ear lobe (site for ear piercing). A section along the dotted line reveals that the ear is composed of cartilage and skin. Cartilage is the internal supporting part and the skin is the covering. The cartilage is elastic as seen in the enlargement. The skin is typical with hair follicles, sweat glands and sebaceous glands as seen in the enlargement. The ear canal leading to the middle ear is 25 mm long and is lined with skin that becomes thinner as the ear drum is approached. Another type of gland, the ceruminous gland, is present. It secretes cerumen or otherwise known as ear wax. The cerumen lubricates the skin of the canal and coats the hairs to impede the entry of foreign particles into the ear. The amount of wax secreted varies from person to person. Some individuals secrete so much wax that it must be cleaned out or hearing is impaired.

sertoli cells blood-testis barrier

The blood-testis barrier is formed by tight junctions between Sertoli cells that segregate the wall of the seminiferous tubule into two compartments - the adluminal compartment, which embraces the spermatids and spermatocytes, and the basal compartment, which embraces spermatogonia. When committed, spermatogonia that are diploid (2n) move from the basal compartment to the adluminal compartment in order to supply more cells for spermatocytogenesis. The tight junctions unzip when the spermatogonia need to move into the adluminal compartment and zip up behind the cell as it migrates from one compartment to another. While the spermatogonia have the normal somatic number of chromosomes, diploid - 2n and do not represent a foreign cell to the body, spermatocytes that are tetraploid - 4 n and the spermatids, haploid -1n are both cells that would be recognized by our immune system as foreign cells. If there was no blood-testis barrier, antigen presenting cells would present their surface molecules to immune cells. There would follow an immune reaction that would destroy the developing sperm cells.

Cervix Mucosa and Glands

The cervix mucosa measures about 2 - 3 mm thick. It differs significantly from the rest of the uterine endometrium. The mucosa consists of simple columnar epithelium with glands projecting into the wall of the cervix. These are mucus secreting glands as illustrated in this slide. While the mucosa itself undergoes little change during the menstrual cycle, the glands increase their secretion about 10 fold at the mid-point of the menstrual cycle. This mucus is less viscous than that secreted at other times during the cycle. It is thought that the less viscous mucus makes it easier for sperm to travel up through the cervical canal into the uterus. The timing is precisely at the time of ovulation.

Corneoscleral Layer

The cornea is continuous with the sclera anteriorly. The sclera is made up of dense collagenous connective tissue as can be seen in the enlargement below the eye image. The cornea is composed of an epithelium, a stroma and endothelium. As can been seen in the enlargement of the outer and inner aspect of cornea, it actually consists of three cellular layers -epithelium, the stroma (consisting of collagen fibrils and fibroblasts) and endothelium. The stroma is composed of around 60 thin lamellae of collagen fibrils embedded in a ground substance. The collagen fibrils form an orthogonal array and the cornea hydration is carefully controlled, both of which are responsible for its transparency (cornea is the 'window' of the eye). In addition there are two non-cellular layers and they are both basement membranes. Bowman's membrane underlies the epithelium and Desemet's membrane underlies the endothelium. The corneal epithelium is a non- keratinized stratified squamous epithelium 50 micrometers in thickness composed of about 5 layers of cells. It has a remarkable regeneration capacity so that it can renew itself in 7 days. There are numerous free nerve endings in the cornea making it very sensitive to touch. Tears, containing water and oil, are very important for keeping the cornea normal and healthy. Bowman's membrane provides strength to the cornea. Descemet's membrane is an exceptionally thick basement membrane that, unlike Bowman's membrane, can be regenerated in case of injury. The corneal endothelium is a single layer of squamous cells that interface with the aqueous humor of the anterior chamber. These cells regulate the water content of the corneal stroma which is very important to maintain transparency.

penis tissue

The corpora cavernosa are two dorsal erectile cylinders penetrated by a deep artery and ensheathed by a thick tunica albuginea of dense connective tissue. At the bottom of the left image is the Corpus spongiosum (corpus cavernosum urethrae) a single smaller cylinder surrounded by a thinner connective sheath. The upper right image shows an enlargement of the corpus spongiosum surrounding the penile urethra. The image below is an enlarged view of the corpus cavernosa shows the vascular blood spaces that become engorged with blood that results in an erection of the penis.

low power histo section HandE

The cortex consists of three zones containing cells with different functions. The zona glomerulosa is thin and the outermost zone. This zone stains more basophilic due to the fact that these cells are small and therefore the staining reflects the crowded nuclei. The zona fasciculata is the widest zone consisting of cells that are lighter stained due to the fact that these cells contain stored steroid that is lipid and therefore dissolves out in preparations using alcohol. The third zone is the zona reticularis. It is rather small and consists of cells with a large component of a brown pigment, a so-called old age pigment. Note the large veins in the medulla. The medulla consists of cells that are generally basophilic.

ductus deferens

The ductus deferens is a direct continuation of the tail of the epididymis. It is lined by pseudostratified columnar epithelium. The wall of the ductus deferens is made up of three layers of smooth muscle oriented differently -inner is longitudinal, middle or intermediate is circular and the outer is longitudinal. The muscle layers are coordinated in their function of propelling the sperm toward the prostate gland by peristaltic waves of muscular contractions.

efferent ducts

The efferent ductules have ciliated cells - the only part of the duct system from seminiferous tubules to the urethra that has motile cilia. The epithelium is composed of alternating patches of ciliated and non- ciliated simple cuboidal and simple columnar epithelial cells.

Vagina: Mucosa

The epithelium of the vagina undergoes cyclic changes during the menstrual cycle. During the follicular phase of the ovary that corresponds to the proliferative phase of the endometrium, under the influence of estrogen, the epithelial cells synthesize and accumulate glycogen (seen as empty spaces in the H&E stained specimen as PAS positive material in the PAS reacted specimen) as they migrate toward the surface. Glycogen feeds lactobacilli, which are bacteria that produce lactic acid. Lactobacillus is a genus of Gram-positive facultative anaerobic or microaerophilic bacteria. They are a major part of the lactic acid bacteria group, named as such because most of its members convert lactose and other sugars to lactic acid. They are common and usually benign. In humans they are present in the vagina and the gastrointestinal tract, where they are symbiotic and make up a small portion of the gut flora. Feeding on the glycogen provided by glycogen laden cells that slough from the vaginal epithelium, the bacteria make lactic acid. This acid lowers pH of vaginal lumen, resulting in protection from other harmful bacteria.

overview of female reproductive system

The female reproductive organs consist of two mammary glands, two ovaries (female gonads), two uterine tubes (oviducts), the uterus, the cervix and the vagina. External genitalia are the clitoris, labia majora and labia minora (not illustrated). The ovaries have two parts, a cortex that encloses a medulla. The uterine tubes are constructed of a mucosa lined with ciliated epithelium that is surrounded by a wall of smooth muscle. The uterus is composed of a special mucosa containing glands and is referred to as the endometrium, the histology of which changes depending upon the blood levels of estrogen and progesterone. The vagina is connected to the uterus at the cervix, a transitional structure. The vaginal mucosa has no glands consisting of stratified squamous non-keratinizing epithelium. The wall of the vagina is a combination of elastic fiber rich connective tissue and smooth muscle. Between menarche (the first menses or first menstrual cycle) and menopause (time in life of female when menses - menstrual cycle - ceases) cyclic changes occur, roughly every 28 days, in the structure and activity of the ovaries and uterus. The coordinated timing of these changes, crucial to normal reproductive function, is controlled mainly by pituitary secretion of Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH). These hormones directly affect the ovaries influencing growth of one to several oocytes and the surrounding follicular cells until one ovum is released by a process known as ovulation.

Snapshots of Uterine Tube Segments

The four segments of the uterine tube each have a different degree of folding of the mucosa. After the fimbriae catch the ovum, the ovum travels in the valleys between the folds. The highest degree of folding is in the ampulla and the least is in the intramural segment. After fertilization in the distal segment of the uterine tube the zygote must make it to the uterus or, otherwise an ectopic pregnancy may occur, i.e. a pregnancy where the embryo implants into the mucosa of the uterine tube. Prior infection of the uterine tubes may cause folds of the mucosa to fuse creating blind 'alleys' so to speak into which the ovum may enter and not be able to continue its journey to the uterus.

Uterus

The human uterus is a hollow pear-shaped organ located in the pelvis between the bladder and the rectum. In a non-pregnant woman, it weighs 30 - 60 grams and measures 7.5 cm in length, 5 cm in width at the most superior aspect and is 2.5 cm thick. Anatomically it is divided into two regions - the body and the cervix. At the upper part of the body where the uterine tubes enter is the region known as the fundus (a blind end). The cervix is the lower, barrel-shaped part of the uterus. The lumen of the cervix, the cervical canal has a constricted opening, the os, at either end. The internal os communicates with the cavity of the uterus and the external os communicates with the cavity of the vagina. The wall of the uterus has three layers. The inner layer is the endometrium that constitutes the mucosa with glands. The middle layer is the myometrium made up of smooth muscle and connective tissue. The outer or third layer is the visceral perimetrium (also named the serosa) covering the entire posterior surface but only a part of the anterior surface, which is covered with an adventitia composed of connective tissue.

the iris and ciliary body

The iris, enlarged on the left, arises from the anterior border of the ciliary body and is attached to the sclera. The iris is a thin disc with a hole, the pupil, in its center. The iris is covered on its posterior surface with a highly pigmented epithelium. The pigment is so dense one cannot see the nuclei in the cells. The anterior surface is covered with modified fibroblasts that resemble epithelial cells and just under that are melanocytes in the stroma. Eye color is influenced by the pigment present in this region. If little or no pigment eye color is blue caused by reflection of light off the posterior pigmented epithelium. As the amount of pigment increases in the stroma eye color changes from blue to shades of greenish blue, gray and finally, brown. The stroma is highly vascularized to supply the smooth muscle that controls the size of the pupil oxygen and nutrients. The muscle that constricts the pupil is located anterior to the posterior pigmented epithelium near the tip end of the iris. The smooth muscle cells that dilate the pupil are arranged radially in the stroma. The ciliary body (continuation of the choroid), enlarged on the right, extends from the ora serrata (the point at which the retina ends and epithelium covering the ciliary body begins) to the root of the iris. The ciliary body consists of two layers. An outer layer of smooth muscle, the ciliary muscle that makes up the bulk of the body, and an inner layer that is vascular extending into the ciliary processes. The zonula fibers are anchored into the basal lamina of the ciliary process epithelial cells. The other end of the zonula fibers connect to the lens. There is a continuous connection between the smooth muscle cells, the ciliary processes, the zonula fibers and the lens. The ciliary epithelium covering the processes secretes aqueous humor and participates in the blood-aqueous barrier.

The Lens of the Eye

The lens is a transparent biconvex organ held by zonular fibers (arranged like the springs of a trampoline and referred to as the suspensory ligament of the lens). The lens has three parts, a nucleus, a cortex and a surrounding capsule. The capsule completely encloses the lens. It is composed of collagen type IV similar to basal laminae and basement membranes. The lens fibers are ribbon- like six-sided prisms containing a protein called crystalline that is synthesized by the lens epithelial cells. The enlargement of the cortex reveals their regular arrangement. In the center the fibers are so dense and the lens so hard, that the histological preparation fails to infiltrate paraffin thorough enough so that the tissue shatters when it is being sectioned as can been seen in the enlarged area of the nucleus. The lens has no blood vessels or nerves. On the anterior surface, underneath the capsule, is a layer of epithelial cells. Only the capsule covers the lens on the posterior surface. These epithelial cells produce the fibers of the lens. The lens grows at its equator. The epithelial cells, during lens growth, located at the equator produce the special protein crystalline that is formed into the lens fibers. The protein crystalline is kept within the cell. The nuclei of some of the lens fibers can be seen in the enlarged equator region. Gradually the nuclei disappear. Growth at the equator is rapid during early development and continues at decreasing rate as the person ages. The lens is nourished by the aqueous humor and the vitreous body. A condition known as 'cataract' develops with age. The lens becomes opaque as illustrated in this photograph of a human eye with an extreme cataract. This person could not see at all. Early formation of cataract causes blurred vision due to reduction in transparency of the lens. Note even that the position of the nucleus (brownish region) has shifted. Because the lens has a very sturdy capsule, an ophthalmologist can make a slit in the capsule in order to introduce an instrument that pulverizes the lens after which the particles are sucked out. Then an artificial lens is inserted that is transparent and the patient can see again.

overview of male reproductive organs

The male reproductive system consists of the external genitalia, the testes that produce the male gametes, which are called sperm (spermatozoa), ducts that transport the sperm to the outside and accessory glands - seminal vesicles and prostate that produces the seminal fluid that combined with sperm form the semen that is ejaculated during sexual intercourse. Instead of following the (yellow brick road) as in the Wizard of Oz, follow with me the yellow arrows to understand the pathway that spermatozoa take from the testis to the outside. Spermatozoa (sperm) are made in the testis. They emerge from the testis via multiple tubes called "efferent ducts" and pass into the "epididymis", a very long convoluted tubule that has a head (the most convoluted or, another term would be coiled portion) and a tail, the portion that is less coiled. The epididymis is continuous with the ductus deferens. The ductus deferens, a very muscular tube, propels the sperm along its course by peristaltic contractions of its muscle. The pathway is through the inguinal canal into the abdominal cavity. Now the "road", or as we say here, the pathway continues up over the bladder and, then curving downward, the ductus deferens enters the prostate. Now the tube receives secretions from two glands, the seminal vesicles and the prostate. The secretion from these glands (seminal fluid) nourishes the sperm to make them motile and also neutralizes the acidity of the vagina. As the tube we are following passes through the prostate, a tube from the bladder joins it. The tube is now called the "prostatic urethra". The prostatic urethra is the conduit from the bladder to the penile urethra to the external environment, but also the conduit for sperm when ejaculated. In the prostate the vas deferens acquires significantly more smooth muscle just before joining the prostatic urethra. These are the ejaculatory ducts. During orgasm, the ejaculatory duct muscle contracts strongly in a wave like manner to propel the semen in a forceful manner out through the penile urethra, a process called ejaculation.

Uterine Tube Wall Structure

The mucosa of the uterine tube is surrounded by smooth muscle, connective tissue, and a covering of the peritoneum, the serosa. The transport of the egg through the tube is not fully understood. Ciliary action combined with peristaltic waves of muscle contraction is the most likely parts of the mechanism.

ovary

The ovary is a solid organ shaped like an egg with a cortex and medulla. It is no more than 5 x 3 cm in size and weighs no more than 5 grams. At the very peripheral aspect of the cortex just beneath the germinal epithelium there is a layer of dense connective tissue, the tunica albuginea, which serves as a capsule to enclose and contain the delicate developing egg cells and the cells of the follicles. The medulla, enclosed within the yellow line, contains connective tissue, special interstitial cells, nerves, lymphatics and blood vessels. The cortex is where human eggs develop. This enlargement of the cortex shows many rounded structures. These are primordial follicles. Further enlargement, upper right, shows that each primordial follicle contains an oocyte surrounded by one layer of flat cells resting on a basal lamina. There are around 400,000 of these primordial follicles filling the cortex at the time ofbirth. Atpubertyseveraloftheseprimordial follicles are stimulated to grow. Normally one of these (although occasionally several) develop into a mature ovum (egg) that is expelled from the ovary by ovulation. This enlargement (lower right) shows the first two stages of development. First the cells surrounding the oocyte enlarge to cuboid shape. These are called granulosa cells. The next stage is a multilaminar primary follicle. The granulosa cells have multiplied and the oocyte has enlarged. Learning the histology of the ovary other than knowing the location and content of the cortex and medulla is learning the stages of ovarian follicle development - folliculogenesis

Mammary Gland: Inactive Lobules

This low (left image) and medium (right image) magnification views of breast tissue shows the histological structure before puberty and post menopause, at which stages the histology is similar. Only ducts are present surrounded by adipose rich connective tissue.

Folliculogenesis

The ovary is covered with a simple cuboidal epithelium that is equivalent to the mesothelium. Traditionally it is called the germinal epithelium, but it has no function in producing germ cells (oocytes and ova). The germ cells, oocytes, migrated into the ovary during embryological development. While oocytes are developing they are surrounded by cells that provide support and secrete hormones that assist in development. In this illustration at the lower right is a primordial follicle, an oocyte surrounded by one layer of cells. Moving to the left there are two stages of development in which the cells surrounding the oocyte (granulosa cells, also called follicular cells) are multiplying so several layers are added. Next to the left is a secondary follicle. This stage is marked by the secretion of a protein rich fluid between the follicular cells. The fluid filled space is called antrum. To the left of this stage the antrum is enlarging until, finally the follicle has matured and is now called a tertiary (Graafian) follicle. The follicle has moved near the edge of the ovary. The oocyte (ovum) is ready to escape from the follicle and the ovary by a process called ovulation. The ovulated oocyte is surrounded by follicular cells will be picked up by the long finger-like projections of the oviduct (fallopian tube). Observe in the center of this drawing two atretic follicles. These are follicles that started to develop but did not make it. After ovulation, the follicle becomes a small endocrine organ-the corpus luteum. Cells in the corpus luteum produce estrogen and progesterone to maintain the endometrium of the uterus that receives the ovum. If fertilization occurs, the corpus luteum continues to develop to play its role, but, if fertilization does not occur, the corpus luteum regresses and is replaced by fibrous tissue forming a scar called the corpus albicans. Next the relationship between pituitary hormones and folliculogensis will be illustrated and explained.

Bulbourethral (Cowper's) Glands

The paired bulbourethral glands are pea sized structures located in the urogenital diaphragm (this is connective tissue and muscle between the bladder and the external environment near the base of the penis). The glands are compound tubuloalveolar glands that resemble mucus secretory glands. The simple columnar epithelium that varies in height depending on its functional state is under the control of testosterone. The clear, mucus like glandular secretion contains galactose, galactosamine, galacturonic acid, sialic acid and methylpentose. Sexual stimulation causes release of the secretion which constitutes the major portion of the preseminal fluid, serving most likely to lubricate the penile urethra.

pancreas relationships

The pancreas is both an exocrine and endocrine gland. The pancreas has a head and a tail. Its head lies in the curvature of the duodenum. The pancreatic Islet cells are derived from the exocrine cell which means the ultimate origin of Islet cells is endoderm. Islets (name means islands of cells) are clusters of endocrine cells that are distributed throughout the pancreas. Islets are represented in this slide by the small blue oval shapes.

penis general structure

The penis comprises three cylinders of spongy erectile tissue surrounded by a common connective tissue sheath and covered by hairless skin. The corpora cavernosa are two dorsal erectile cylinders penetrated by a deep artery and ensheathed by a thick tunica albuginea of dense connective tissue. Corpus spongiosum (corpus cavernosum urethrae) is a single smaller cylinder surrounded by a thinner connective sheath. Its expanded distal tip is the glans penis. It is penetrated along its entire length by the cavernous (penile) urethra.

prostate gland stroma

The prostate gland has a fibromuscular stroma that surrounds the glands. Within this stroma are smooth muscle cells so that the entire gland is able to squeeze and thereby emptying the secretions of the gland into the urethra. The secretions of the prostate include fibrinolysin, citric acid and a serine protease, clinically known as PSA (prostate specific antigen). Levels of PSA in the blood may suggest an enlarged prostate gland. The alveoli of prostate glands, especially in older men, often contain prostatic concretions (corpora amylacea) of varied shape and size up to 2 mm in diameter. They appear in sections as concentric lamellated bodies. They are believed to be formed by precipitation of secretory material around cell fragments and they may become partially calcified.

Prostate Gland General Structure

The prostate gland is the largest of the accessory glands. Its size and shape are similar to a walnut. It is located in the pelvis just inferior to the bladder. It surrounds the prostatic urethra. It consists of 30 - 50 tubular alveolar glands that are represented by the blue outlined spaces in the drawing on the left. The image on the right is a section through the whole prostate, a cross-section that shows the urethra. The many empty spaces are the lumens of the glands.

Hypothalamo-Hypophyseal Portal System

The release of hormones from the acidophils and basophils of the Pars Distalis is under the influence of releasing factors that are released by neurons in the hypothalamus. These neurons release the factors into capillaries in the hypothalamus fed by superior hypophyseal arteries. These capillaries are drained by veins called the hypothalalmic-pituitary portal veins. These portal veins carry blood to the pars distalis and the releasing factors end up in capillaries. This constitutes the hypothalamohypophysial portal system. Note that the capillaries/sinusoids in the anterior lobe have fenestrations with diaphragms that make it easy for releasing factors to reach the cells of the adenohypophysis and also for the hormones secreted there to enter the vascular system. One example is given of a releasing factor, TH-RF (thyroid hormone releasing factor, or also called Thyrotropin Releasing Hormone) that is transported by the portal system to reach and act on basophils of the anterior pituitary causing them to release TSH (thyroid stimulating hormone). The basophil can also be referred to as a Thyrotroph because it has a trophic effect on the thyroid gland. The releasing factor in this case can also be referred to as a Thyrotropin. Thyrotroph is a cell and thyrotropin is a molecule.

Endocrine internal secretions without ducts

The secretion of an endocrine gland is delivered to internal organs/tissues/cells via the circulating blood. Classically the term endocrine refers to a substance, a hormone that is secreted by one cell, travels via the blood stream to affect another cell. That was the first concept that was discovered. However further investigation over many years has brought about a fuller understanding of endocrine secretions in the body. e.g. thyroid hormone secreted by the thyroid gland & delivered by blood vessels influences metabolism by cells of many organs

feedback regulation

The secretion of endocrine organs is regulated by feedback from the target organs, tissues or cells. This regulation is by either positive or negative feedback. When the response to a hormone by a target tissue results in more of the hormone being produced by the endocrine gland that is positive feedback. When the response to a hormone by a target tissue results in less of the hormone being produced by the endocrine gland that is negative feedback. Negative feedback is more common in the endocrine system. For example let's consider the relationship between the pituitary gland and the thyroid gland. The pituitary gland secretes thyroid stimulating hormone (TSH) that, when it reaches the thyroid gland, causes the cells to produce more thyroid hormone. This results in an elevation of the level of thyroid hormone in the blood. When the pituitary cells that produced the TSH are bathed in this elevated level of thyroid hormone, they produce less TSH. This is negative feedback. This is analogous to a home heating and air conditioning system. For example the temperature of the home is controlled by a thermostat. If the existing temperature in a home is 80 degrees and the desired temperature is 78 degrees, a signal is sent by the thermostat to the compressor to generate more cool air. When the temperature in the home reaches 78 degrees the thermostat sends back a signal to shut off the compressor. This is negative feedback.

Accessory Glands Seminal Vesicles, Prostate & Bulbourethral Glands

The seminal vesicles are located on either side of the bladder. They empty by their ducts into the ductus deferens within the prostate gland. The Prostate gland is situated below the bladder. The bladder drains through the prostate and its duct receives both ejaculatory ducts. The bulbourethral glands are located on either side of the base of the penis. Their ducts drain into the beginning of the penile urethra. All three of these glands contribute to the seminal fluid that nourishes the sperm.

Seminiferous Tubule Components

The seminiferous tubules are like secretory units. They secrete whole cells, the sperm. In this sense the testis is an exocrine gland and secretes by the holocrine method. Each tubule is highly convoluted and packed into a small space. The walls of each tubule, from the exterior to the lumen, are composed of three layers. The tunica propria is a thin tunic of fibrous connective tissue with several layers of fibroblasts. The innermost layer includes contractile myoid cells that attach to the basal lamina. A well- defined basal lamina separates the tunica propria and the seminiferous epithelium. The stratified seminiferous epithelium consists of two cell lineages: spermatogenic cells and supportive cells (Sertoli). Spermatogonia cells - small round cells near the basal lamina. They are the least differentiated and are the only spermatogenic cell present before puberty. Sexual maturity occurs when progeny from these cells make sperm cells. Spermatogonia are diploid - they have 46 chromosomes, 2N. They will divide and give rise to other spermatogonia and to: Primary spermatocytes: that become closer to lumen than spermatogonia. They are the largest cell present in the seminiferous tubule; each has a large nucleus with dark strands of heterochromatin. They are seen in prophase I of meiosis. They are diploid for chromosome number but immediately prior to division they are 4N. Secondary spermatocytes appear and disappear quickly because as soon as they form they immediately undergo meiosis II to give rise to Spermatids, which are located next to the lumen. Small cells with dark heterochromatic chromatin. They are haploid 23 chromosomes and 1N. This whole process from the stem cells, spermatogonia transforming into primary spermatocytes, then secondary spermatocytes, then into spermatids, and finally into sperm is called SPERMATOGENESIS. There are three phases: spermatogonial phase, spermatocyte phase and spermatid phase.

thyroid and parathyroid

This drawing shows in more detail the location of the thyroid. Also, the blue areas in the thyroid in this drawing indicate the location of the parathyroid glands. Parathyroid glands number on the average four glands, two on either side. They share the capsule of the thyroid gland as you can observe in the histological section on the right. Note the difference in the patterns of the two glands. Both glands are classified as solid organs without a cortex or medulla.

Stria Vascularis Electron Microscopy

This electron microscopic enlargement of the stratified columnar epithelium of the stria vascularis demonstrates the presence of capillaries within the epithelium. Genetically modified mice are now being used to investigate just how this epithelium functions to produce the endolymph in the scala media and what affect atrophy of the stria vascularis might have on hearing.

The Vestibular Apparatus

The sensory receptors of the membranous labyrinth of the vestibular apparatus sense angular movement, gravity and acceleration. The vestibular apparatus consists of canals, ducts and special structures called utricle and saccule. There are three semicircular canals housing the semicircular ducts. Each canal containing a duct has a swelling near its connection with the vestibule. They are called ampullae. In each duct portion of each ampulla there is a special arrangement of cells and extracellular substances called a crista ampullaris. This drawing illustrates a single crista with its appearance in a histological specimen next to it. The crista is a ridge shaped structure composed of sensory hair cells with stereocilia and a single cilium on each cell. A gelatinous protein-polysaccharide mass, called the cupula, is attached to the hair cells. Nerve endings connect to the base of each hair cell. During movement the walls of the canals move first but the endolymph inside lags behind. This lagging of the endolymph creates a current. The cupula is swayed by the flowing endolymph. Deflection of the stereocilia with reference to the single cilium by the cupula generates nerve impulses. The horizontal canal is aligned roughly horizontally in the head. The superior and posterior canals are aligned roughly at a 45 degree angle to a vertical plane drawn from the nose to the back of the skull. Thus, the horizontal canal detects horizontal head movements, while the superior and posterior canals detect vertical head movements. The movements detected are analogous to the roll, pitch and yaw of an airplane as illustrated here. Pitch is analogous to looking up or down. Roll is analogous to tilting the head to one side or another. Yaw is analogous to turning the head in a horizontal plane. The vestibular apparatus detects all motions between these three. Gravity and linear acceleration / deceleration are detected by sensory hair cells in the saccule and utricle. They are a part of a structure called the macula. The macula is a flat structure that contains sensory hair cells that are covered with a gelatinous structure. The gelatinous structure is called the otolithic membrane. Its outer surface contains 3 - 5 micrometer crystalline bodies of calcium carbonate. These bodies do two things. They press on the hair cells and the result is the sensation of gravity. They drag along the hair cells when one is linearly accelerating or decelerating. The vestibular nerve collects the axons from the nerves in the vestibular apparatus and conducts the impulses to the brain.

thyroid anatomy

The thyroid gland has two lobes and an isthmus between the two lobes. The two lobes lie on either side of the trachea just below the thyroid cartilage at the level of the cricoid cartilage, the first cartilage of the trachea. To palpate the thyroid gland, find your Adam's apple (thyroid cartilages) and place your thumb and index finger on either side. Now slide your thumb and index finger down about one inch. The lobes of the thyroid lie just beneath your thumb and index finger. If the thyroid is enlarged you will feel it. If not, you will not be able to feel it. Enlargement of the thyroid also shows up in the midline. Just looking at a person after asking them to swallow will reveal an enlargement crossing from side to side if the thyroid is enlarged.

The Thyroid Follicle: functional unit

The thyroid gland is composed a repeating functional unit called the thyroid follicle. It is a spherical shaped structure that has a wall of simple squamous, cuboidal or columnar epithelium depending upon the functional state of the follicle. The follicles range from 0.2 to 1.0 mm in diameter. There are many thousands in the gland. As illustrated in the drawings each follicle is surrounded by a dense capillary bed that serves to bring raw materials to the epithelial cells to make the thyroid hormone, and to carry away the thyroid hormone to target tissues and organs. Each follicle contains the stored form of the hormone, the colloid.

thyroid follicle histology

The thyroid gland is the only endocrine organ that stores its hormone in an extracellular compartment. To retrieve the stored hormone the follicular cell must phagocytize a portion of the colloid and then break it down. The scallop border, when present, in a thyroid follicle, is evidence of this phagocytic activity. In both images there are several active follicles as evidenced by the cuboidal cells and the scalloped border of the follicle colloid. In the left image two follicles are inactive as evidenced by the absence of a scalloped border and the follicular cells are low cuboidal in shape and even several follicular cells are squamous as indicatedbythearrows. Intherightimageaparafollicular cell is indicated. This cell is also called a C-cell which stands for clear cell. Observe that it is intimately associated with the nearby follicular cells and that its cytoplasm has not reacted with either hematoxylin or eosin. The C-cell synthesizes and secretes a different hormone, calcitonin that lowers blood calcium by reducing intestinal absorption of calcium and inhibiting the activity of osteoclasts in bone.

Straight Tubules (tubuli recti)

The transition from the seminiferous tubule through the straight tubule into the rete testis involves first the presence only of columnar Sertoli cells without the developing sperm cells. As one approaches the rete testis in the straight tubules the epithelium becomes cuboidal and the tight junctions move from a more basal location to an apical location between the cells.

Testis Capsule, Lobules & Mediastinum

The tunica albuginea (A) is the capsule of the testis. It is composed of dense collagenous connective tissue. Its outer surface is covered with mesothelial cells forming the inter part of the tunica vaginalis. Recall from the last slide that the fibrous septae which separate the testis into as many as 300 lobules (L) converge at the mediastinum (M) in the posterior margin of the testis. Note the profiles within the lobule (L). These are sections through the coiled seminiferous tubules. The next slide will show an enlargement of this rectangular area that will present the seminiferous tubules at higher magnification.

Stria Vascularis Specimen: Cochlea of a Guinea Pig

This histological specimen of the cochlea is from a guinea pig. Observe the sections through the cochlear canal. Look carefully at the stria vascularis indicated by the arrows in each of the profiles of the canal. Observe that the stria vascularis has picked up the eosin stain. In the enlargement of one of the cross-sections of the cochlear canal you can see that the stria vascularis is eosinophilic because of erythrocytes within the intraepithelial capillaries. The tissue underlying the epithelium is a modified connective tissue that serves as a channel for the blood supply to the epithelium. Stria Vascularis is a vascularized stratified columnar epithelium covering the inner surface of the spiral ligament. It is the only vascularized epithelium in the body. It produces and maintains the endolymph of the scala media. The next slide will present an electron micrograph of the epithelium of the stria vascuaris.

Pituitary Adenoma & Optic Nerve

This is a photograph taken at autopsy showing a gross anatomical view of a pituitary adenoma. Note the close relationship between the pituitary gland the optic nerve. A pituitary tumor may enlarge to the point that it can affect the optic nerve causing a defect in vision. In such cases the adenoma must be surgically removed

External Eye lids, lashes & glands

The upper and lower eyelids are covered with skin on the outside and the palpebral conjunctiva on the inside. The conjunctiva, both bulbar and palpebra is a thin transparent mucous membrane composed of stratified columnar cells with goblet cells and an underlying lamina propria of loose connective tissue with blood vessels. The goblet cells in the conjunctival epithelium contribute to the composition of tears. The stiffness of the eyelids is due to the tarsal plates that are composed of dense collagenous connective tissue. They are crescent- like plaques that make up a 'so-called skeleton' of the eyelids. Meibomian glands are embedded within and outside of the tarsal plates. Meibomian glands are sebaceous glands not associated with any hair follicles that empty their oily secretions onto the surface of the eye via the pores that can be seen in the lower left image as tiny white dots. One of the ducts that connect to a pore is labeled in the histological specimen. The upper surface of the eyelid covered with skin contains hair follicles that are the eyelashes. Between the tarsal plate and the skin are the muscles that close and open the eye. These are composed of striated skeletal muscle cells and are under voluntary control. Meibomian gland ducts can become clogged and that results in a swelling that, if it does not go away, an ophthalmologist must lance it with a scalpel to let the accumulated secretions escape. These are called chalazions or meibomian cysts. Usually they do not become infected. The swelling is just the accumulation of oily secretory product in the duct. The sebaceous glands associated with the hair follicles of the eyelashes can become infected resulting in a local swelling of the eyelid called a stye. Meibomian cysts are not painful, but styes are due to the infection. Both can be treated.

Uterine (Fallopian) Tubes

The uterine tubes (oviducts or Fallopian tubes) begin very close to the ovaries and terminate in the wall of the uterus with their lumens connecting to the lumen of the uterus. Each uterine tube is about 10 - 12 cm long. The very beginning of the tube that is very close to the ovary is the fimbriated end containing numerous fimbriae - finger like projections containing a core of smooth muscle - connective tissue that is covered by a ciliated simple columnar epithelium. The fimbriae move during ovulation creating a current in the peritoneal fluid to facilitate catching the ovum. The remainder of the tube is in four parts - the infundibulum, the ampulla, the isthmus and the segment that goes through the muscular wall of the uterus at the end of which the lumens of the uterine tubes are continuous with the lumen of the uterus.

vascular coat and layer

The vascular coat of the eye includes the iris, ciliary body and the choroid. The enlargement on the left illustrates the iris and ciliary body. Observe that the cornea is continuous with the sclera. The enlargement on the right illustrates the third component of the vascular layer, the choroid. Observe the blood vessel. Lining the inside of the eye at this point is the two layered epithelium of the retina. The pigmented epithelium lies just outside of the nonphotosensitive retina epithelium in the anterior 2/3 of the eye globe. The two layers of the choroid are the choriocapillary layer (where you see the blood vessel) and Bruch's membrane. Bruch's membrane has five layers: two basal laminae - one facing the choriocapillary layer and one facing the pigmented epithelium. Between the two basal laminae is a layer of elastic fibers sandwiched in between two layers of collagen fibers. Bruch's membrane is only about 4 micrometers thick. It runs from the optic nerve to the ciliary body.

parathyroid HandE stain

There are two cell types in the parathyroid gland. Chief cells are the most numerous and they are the cells that produce the parathyroid hormone (also called parathormone). The other cell type is the oxyphil cell that is intensely acidophilic due to the large number of mitochondria located in its cytoplasm. No function for these cells in the normal parathyroid gland has been determined. They appear in clusters and these clusters of oxyphil cells increase with age. Adipose tissue also increases with age in the parathyroid gland

pars distilas HandE stain

This histological specimen of the pars distalis of the adenohypophysis is at a fairly high magnification where you can see the differentiation between basophils (blue stained), acidophils (red stained) and chromophobes (no stain). Acidophils and basophils synthesize and release various hormones. The chromophobes are thought to be either acidophils or basophils caught during fixation at the stage where the cells have just been depleted of their stored hormones. Observe the sinusoids that contain erythrocytes. The sinusoids are fenestrated vessels.

Interconnectivity of Developing Sperm Cells

This illustrates the interconnectivity of a clonal population of cells that are developing into sperm. Note the proliferation of several generations of spermatogonia and the eventual differentiation into type B which then form the primary spermatocytes. It takes about 16 days for proliferating spermatogonia to become committed as type B. Each of the other three phases lasts around 16 days resulting in a time course of 64 days from spermatogonia to sperm. At any given location along the length of a seminiferous tubule there will be different stages in the development of sperm. For example at one location there may be mostly primary spermatocytes and at another mostly spermatids, and at another location mostly spermatocytes. Note very carefully the bridges drawn between all of the cells in the various stages. This cytoplasmic bridge makes all of these cells a syncytium. The cytoplasmic bridges and excess cytoplasm is removed by sertoli cells at the last stage of transformation from spermatid to sperm resulting in sperm that are separated.

Organ of Corti Function

This is a drawing of a cross-section of the cochlear canal that contains the organ of Corti. The oval dotted line defines the location of the organ of Corti. Let's begin an explanation of its function with sound waves striking the tympanic membrane. The vibrations set up by the oscillation of the ossicles of middle ear and converted into fluid movement via the oval window of the cochlea arrive in the chambers of the cochlea. The movement of fluid in the perilymph of the scala vestibuli is transmitted through the Reissner's membrane into the scala media where the organ of Corti is housed. The enlargement of the organ of Corti below illustrates the cells and structures of which it is composed. It is a spiral organ meaning that it follows the spiral of the helix of the cochlea. It is the receptor organ of hearing. The sound vibrations as fluid oscillations are transmitted through Reissner's membrane travel through the scala media endolymph and impact the basilar membrane causing it to oscillate. The oscillations travel in waves in the basilar membrane. The tectorial membrane forms the roof of the organ of Corti and the basilar membrane forms its floor. In the spiral organ of Corti there are inner and outer hair cells, and inner and outer phalangeal (supporting) cells. Hair cells are attached through supporting cells to the basilar membrane that vibrates during sound perception. The stereocilia of these hair cells are in turn attached to the tectorial membrane that also vibrates. The tectorial membrane and the basilar membrane are hinged at different points in the scala media and therefore, during vibrations, the hair cells are subjected to a shearing force that in turn generates a signal that is transmitted to the cochlear nerve ends around the hair cells. The drawing on the right shows the location of high and low frequency vibrations of the basilar membrane. After transduction occurs by the interaction of the hair cells with the nerve endings sound information is sent to the brain as an electrical signal transmitted by the cochlear nerve. Age- related hearing loss, or presbycusis, is the slow loss of hearing that occurs as people get older. One of the most common effects in hearing loss occurs mostly in males and that is the loss of hear high frequency sounds. An excellent narrated animation of sound conversion and transduction by the organ of Corti can be accessed by pausing this lecture and clicking on the screen capture from the video.

Retinal Layer

This is a histological section near the optic cup (papilla) where all three layers of the eye can be seen - the retina, the choroid and the sclera. The neuron cell component of the retina thins as it approaches the optic cup and the optic nerve fiber layer thickens because of the tremendous number of axons that are about to enter the optic nerve. The nerve fascicle is a part of one of the nerves that innervate the extraocular muscles of the eye - the muscles that move the eyeball in all directions.

neurohypophysis with a trichrome stain

This is a histological section of the pars nervosa stained with a trichrome stain. Observe one Herring body, one of the many, many storage locations of ADH and Vasopressin.

the testis

This is a histological section through the testis shown at low magnification that presents a panoramic view. It is a solid organ with no cortex or medulla. The testis weighs about 15 grams and its dimensions are on the order of 4.5 cm long and 2.5 - 3 cm wide. The sperm manufacturing element of the testis consists of the seminiferous tubules that are individual tubules that connect with the rete testis in the mediastinum. This parenchymal element, the seminiferous tubules are organized into groups of up to 4 enclosed by a connective tissue septum and this is a unit called a lobule. There are as many as 300 lobules in the testis making it possible for a single testis to contain as many as 1200 seminiferous tubules. In the drawing more detail can be observed. First, the testis is wrapped in skin called the scrotum. The scrotum is actually a sac containing a diverticulum of the abdominal cavity with its peritoneum. The testis is wrapped with a dense connective tissue capsule called the tunica albuginea. Groups of up to four seminiferous tubules are separated by connective tissue septa creating lobules. The seminiferous tubules in each lobule loop from and back to the mediastinum where they connect with ducts leading from the testis. The duct complex at the mediastinum consists of straight tubules connected directly to the seminiferous tubules, then the efferent ducts leading to the head of the epididymis. Then the convoluted tubule making up the epididymis courses through a body and tail region and emerges as a single now stretched out tube called the ductus deferens. Observe the drawing at the lower left where you can see that, during development, the testis begins in the abdominal cavity of the fetus. At some point during development the testis descends, guided by a ligament, the gubernaculum. As the testis descends along the back wall of the abdominal cavity it carries some peritoneum with it that forms a process, the processus vaginalis. This passes through the future inguinal canal. Finally, in the adult descended testis, the tunica vaginalis was formed from the processus vaginalis. Note that the tunica vaginalis is a mesothelium lined sac derived from the peritoneal cavity. It contains a small amount of peritoneal fluid. It is important for the testis to have descended to be in an environment of cooler temperature than the abdominal cavity, a requirement for viable sperm.

pancreas survey view

This is a panoramic view of a histological section of the pancreas. The islets of Langerhans are the lighter stained mostly oval shaped structures. The letter I lie in the main pancreatic duct that empties the gland of its exocrine secretion into the duodenum. The asterisks are in blood vessels.

external eye

This is a photograph displaying a frontal view of the eye close-up. First observe the pupil where light enters the interior of the eye to interact with the photoreceptorsoftheretina. Thediameterofthe pupil is controlled by two groups of muscles in the iris. The iris is a disc shaped structure composed of loose connective tissue, smooth muscle and covered by epithelium. Its function is similar to the diaphragm in a camera that controls the quantity of light that falls on film or a charge coupled device (CCD) in a digital camera. The pupil is made smaller in diameter by the constrictor muscle in the iris, which is a population of smooth muscles cells arranged circumferentially in the iris near its border with the pupil. The pupil is made larger in diameter by the dilator muscle in the iris, which is a population of smooth muscle cells arranged radially and attaching at the limbus. The limbus is the border between the cornea and the conjunctiva. The conjunctiva is a thin transparent mucous membrane and an underlying lamina propria of loose connective tissue with blood vessels. The goblet cells in the conjunctival epithelium contribute to the composition of tears. There are two components or regions of the conjunctiva - the bulbar conjunctiva that covers the white of the eye and the palpebral conjunctiva that lines the inside of the eyelids. The white of the eye is caused by light reflecting off of the sclera, one the layers of the eye globe that is composed of dense collagenous connective tissue. The cornea is the 'window of the eye'. Even though it is composed of fibers of a type of collagen, due to their arrangement and controlled hydration, the cornea is transparent.

pituitary saggital section

This low power histological section stained with H&E illustrates the different parts of the pituitary gland. The gland consists of two main parts: the adenohypophysis and the neurohypophysis. The adenohypophsis includes the pars tuberalis, the pars distalis and the pars intermedia. The neurohypophysis includes the infundibular stem and the pars nervosa. In the pars distalis the reddish patches are blood vessels containing erythrocytes. Note that the pars distalis has a richer supply of blood vessels when compared to the pars nervosa as evidenced by the lighter staining of the pars nervosa. The pars tuberalis and intermedia are minor parts of the adenohypophysis. The adenohypophysis has an indirect connection to the hypothalamus via blood vessels of a portal system that will be explained later in this lecture.

Mammary Gland: Lactating

This slide illustrates a low and higher magnification of a specimen from a lactating breast. The lactating breast has secretory units that are dominated by large alveoli very similar to apocrine sweat glands, only these cells are producing milk protein and fat. At birth the sudden loss of estrogen and progesterone from the placenta and corpus luteum is replaced by prolactin from the anterior pituitary gland that has a lactogenic effect. The secretion released in the first few days after childbirth is known as colostrum. This premilk is an alkaline, yellowish secretion with a higher protein, vitamin A, sodium and chloride content and a lower lipid, carbohydrate, and potassium content than milk. Another most significant component of colostrum is antibodies from plasma cells in the loose connective tissue surrounding the secretory alveoli. The same mechanism that is used by salivary gland cells results in secretory IgA. After a few days the colostrum is replaced by milk.

endocrine gland distrubution

This slide illustrates the distribution of endocrine glands and other organs that secrete hormones along with the parenchymal cells in those organs that synthesize the hormones. the pituitary gland cells include acidophils, basophils chromophobes and Herring bodies, the thyroid gland cells include thyroid follicular and parafollicular cells, the parathyroid gland- chief cells, the adrenal gland cells include cells of three zones in the cortex- glomerulosa, fasciculata and reticularis and also chromaffin cells of the adrenal medulla, and the pineal gland with its pinealocytes (not shown on this slide). Other organs secrete hormones but they have other functions as well. They are the pancreas, testis and ovary. The histology of the testis and ovary will be presented in separate lectures. Feedback mechanisms are integral to understanding endocrine organ functions. acidophils, basophils, chromophobes, Herring bodies chief cells zona glomerulosa cells zona fasciculata cells zona reticularis cells chromatin cells ovarian follicular cells Lydia cells alpha cells beta cells thyroid follicular cells parafollicular (C) cells

parathyroid functions

This slide illustrates the function of parathyroid hormone (parathormone) and contrasts it with the function of the thyroid gland C-cells. Parathormone stimulates osteoclasts, reduces excretion of calcium by the kidney and increases absorption of calcium by the intestines, thus raising the calcium level in blood. Calcitonin by suppression of osteoclast activity, by facilitating movement of calcium from blood into bone matrix by osteocytes and by inhibiting calcium absorption by the small intestine, lowers blood calcium. Therefore, these hormones are antagonistic.

suckling reflex and oxytocin

This slide illustrates the suckling reflex that involves release of oxytocin from the pars nervosa Herring Bodies. It goes like this. First the breast feeding infant sucks on the mother's breast nipple. The sensory nerves in the nipple pick up that stimulus leading next to a sensory response via those nerves that terminate in the supraoptic and paraventricular nuclei of the hypothalamus. Once these are activated they send an impulse via the axons of these neurons to the terminals in the pars nervosa where oxytocin is released. Oxytocin is then transported via the blood to the breast blood vessels where it leaves the blood stream and bathes the myoepithelial cells surrounding the secretory alveoli and ducts of the breast. A synchronized massive contraction of myoepithelial cells squeezes milk out of the nipple into the infant's mouth.

Mammary Gland Changes Summarized

This slide provides a summary of the changes that occur in the female mammary gland. A: In non pregnant women, the gland is quiescent and undifferentiated, containing only ducts that are inactive. B: During pregnancy, alveoli proliferate at the ends of the ducts and prepare for the secretion of milk. This also is the case during the menstrual cycle when estrogen and progesterone levels rise but, without fertilization of an ovum, the changes revert to the non-pregnant state. C: After childbirth the gland is mature with fully developed large alveoli and milk secretion is abundant. Once breast feeding is terminated, the gland reverts to the non pregnant condition.

summary of pituitary gland secretions

This slide serves to summarize the secretions of the pituitary gland. Neurons in the hypothalalmus secrete releasing factors at their terminals in the median imminence of the hypothalamus. These secretions are picked up by capillaries there and transported by the hypothalamic-hypophyseal portal veins to sinusoids in the pars distalis of the anterior pituitary gland. The releasing factors affect the acidophils and basophils in the pars distalis to secrete hormones. Neurons in the supraoptic and paraventricular nuclei synthesize two hormones, oxytocin and antidiuretic hormone. These hormones are transported down the neuron axons to the posterior pituitary gland where they are stored in Herring bodies, from which they are released into the blood stream.

the ovarian cycle

This slide shows the interrelationship of the developing follicles, ovulation and the post ovulation structure, the corpus luteum to the level of Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) from the anterior pituitary. Follicle stimulating hormone from the pars distalis of the adenohypophyisis stimulates several primordial follicles to begin developing by oocyte size increasing and follicular cells dividing. The follicle cells that surround the developing oocytes begin to secrete estrogen. Estrogen acts on the mucosa of the uterus to begin its preparation for receiving a fertilized egg. Ovulation is stimulated by a surge in luteinizing hormone (LH) from the pars distalis of the adenohypophysis. Following ovulation, the additional secretion of progesterone by the cells of the corpus luteum continue to influence the development of the uterine mucosa, first, by estrogen to cause the glands to increase in thickness and then, by progesterone the gland cells grow taller and secrete nourishing substances to ready the uterine endometrium for receiving a fertilized egg and implantation at the beginning of pregnancy. In the next few slides the detailed histology of the developing follicles will be presented. This whole process is called the ovarian cycle.

The Endometrial Cycle

This slide shows the relationship between the endometrial stages and the blood levels of estrogen and progesterone. Simplistically, there are two stages - proliferative and secretory. If an ovum is not fertilized, then the two hormone levels fall off sharply resulting in constricted arteries that cause ischemia and hypoxia of the endometrium. The functional part of the endometrium becomes necrotic and sloughs off with some bleeding, the menstrual phase -often considered to be a third phase.

structure and function of beta cells

This slide, the last slide in this lecture on endocrine organs is presented to illustrate a known time course in the synthesis of insulin. This time course is not identical to that in all other endocrine organ cells, but would be comparable. Observe that the beta cells in the islets are constantly exposed to glucose and this serves to regulate the amount of insulin that is released by the beta cells. Insulin is a protein so the raw materials for synthesizing insulin are amino acids. Some influence of innervation is present upon the beta cell. It takes about one hour for amino acids to be incorporated into a molecule of insulin stored in secretory granules in the beta cell. Unless, for some reason, beta cells are entirely depleted of all stored insulin, there is always insulin ready to be released by beta cells. Even if beta cells are fully depleted, it takes just one hour to replenish a supply of insulin. The endocrine cells of the body are fine tuned to titrate just the right amount of hormones we need to carry out our daily normal functions. No artificial administration of hormones by prescription can compete with this finely tuned regulation. Therapy can only be expected to approach normality, never achieve it.

External Eye Eyelid Muscles

Two muscles of facial expression, the orbicularis oculi and the levator palpebrae close and open the eyelids, respectively. Both of these muscles are composed of striated skeletal muscle fibers and are, as you know, under our voluntary control. The orbicularis oculi muscles are innervated by cranial nerve 3 and the levator palpebrae muscle is innervated by cranial nerve 7, the same nerve that innervates the other muscles of facial expression enabling humans to smile, frown etc. The orbicularis oculi muscle is arranged circularly around the eye. Any neurological condition that affects cranial nerve 3 would interfere with closing the eye. The levator palpebrae muscle is attached with tendons into the connective tissue of the eyelid. Any condition that affects cranial nerve 7 would make it difficult to open the eye resulting in eyelid droop.

Auditory Apparatus Cochlea & the Organ of Corti

Vertical Section 35 mm spiral membranous labyrinth 2 3⁄4 turns of the coiled cochlear duct. The cochlea is a cone-shaped helix that is connected to the vestibule. This is a colored drawing of how it would look if sectioned through from its base to its apex. Between its base and the apex it makes about 2.75 turns around a central core of spongy bone called the modiolus. Within the modiolus lies a sensory ganglion. The colored drawing shows the relationship of the scala media, scala vestibuli and the scala tympani, all of which are spaces filled with fluid. The scala media is the space in the cochlear duct and it contains endolymph. The scala vestibuli and tympani contain perilymph. The red arrow points in the direction of the oval window and the blue arrow points toward the round window. The two scala communicate with each other via a small channel called the helicotrema at the apex of the cochlea. The scala vestibuli begins at the oval window and the scala tympani ends at the round window. This histological section is cut through the 2 3⁄4 turns of the cochlea. First, note the ampulla of a semicircular canal below in which a cristi ampullaris is indicated by the arrow. The drawing on the right is an enlargement of one of the cross-sections of the cochlear canal. The dotted oval delineates the cochlear duct. The duct divides the cochlear canal into three compartments- scala media in the cochlear duct, scala vestibuli above and scala tympani below. The scala media is an endolymph-containing space that is continuous with the lumen of the saccule and contains the spiral organ of Corti. Observe the stria vascularis. It is an epithelium that contains blood vessels with the epithelium. It is responsible for the production and maintenance of endolymph. It is the only epithelium in the body that contains blood vessels. The next slide will present some details of the stria vascularis.

Tears Production & Drainage

Watery component of tears Lacrimal gland > flows over eye surface > collected by lacrimal canaliculi > drain to nasal cavity via the lacrimal sac and the nasolacrimal duct The contribution of a watery secretion to tears is made by the lacrimal gland that contains serous acini as you can see in this histological specimen. The lacrimal glands are located beneath the conjunctiva on the upper lateral side of the orbit of the eye. The secretions flow out of the lacrimal gland in 12 ducts that open at the border between the bulbar and palbebral conjunctiva. Tears flow over the surface of the eye in a film. Tear drainage occurs at the corner of the eye near the nose by two tiny canals called lacrimal canaliculi. There are many myoepithelial cells surrounding the acini and ducts so that, when, it is needed a flood of watery tears pours out over the surface of the eye and may spill onto the surface of the face as in extreme eye irritation or crying. (recall that myoepithelial cells contract to squeeze out gland secretions) Fromthelacrimalcanaliculitearsdrain into the nasal cavity via the lacrimal sac and the nasolacrimal duct. Normally the tear fluid in the nasal cavity is rapidly taken up by the respiratory epithelium. One of the important functions of tears is to wet the surface of the cornea. If the cornea becomes dry vision is blurred.

select all that are true regarding the function of the thyroid follicular cell

all of them

chemically, hormones can be which of the following

all of the above

regarding the flow of aqueous humor, which is out of order fro the site of production to entrance into a blood vessel?

anterior chamber and posterior chamber

make the correct association between the eye chambers and their boundaries

anterior chamber: between cornea and iris vitreous chamber: between lens and retina posterior chamber: between iris and lens

Vagina Wall Histology

arrows are pointing to collagen fibers and then smooth muscle fascicles Mucosa Stratified squamous non- keratinized No mucculris mucosa Lamian propria Collagen fibers some elastic fibers Muscularis Externa Smooth muscle fascicles Compare the trichrome and H&E stained specimens in this slide. It is obvious from observing the trichrome stained specimen that the wall of the vagina is very rich in collagen. The vagina is a fibromuscular sheath extending from the cervix to the vestibule, the area between the labia minora. The mucosal layer of the vagina consists of numerous transverse folds and is lined with stratified squamous non-keratinized epithelium. The lamina propria is rather thick and is composed of mostly collagen fibers with some elastic fibers. The vagina can expand by stretch of the collagen and elastic fibers. The muscularis layer is organized into an inner circular and outer longitudinal layer. The smooth muscle can decrease or increase the lumen size. This combination of muscle and elastic fibers serves the function of receiving and interacting with the penis during sexual intercourse. At the external entrance to the vagina there is a striated muscle under voluntary control called the bulbospongiosus muscle. The vagina does not have any glands

where are the glands that contribute mucus into the lumen of the vagina

cervical mucosa

which of the following cells produces a hormone that raises blood pressure

chromaffin cell

pars distilas anatomy

circle encloses a group of cells which represent a cross-section through a cord of pars distalis secretory cells This slide illustrates the histological architecture of the adenohypophysis. The cells are arranged in cords with sinusoids between. The sinusoidal capillaries in the pars distalis are fenestrated with diaphragms for easy entrance of secreted hormones into the blood vessels for transportation to target tissues.

in a graafian follicle, what connects the oocyte to the stratum granulosum

cumulus oophorus

what is the name of gelatinous structure made up of protein and polysaccharides that is attached to the sensory hair cells of the crista ampullaris

cupula

autocrine

e.g. Helper T-cell proliferation by interleukin- 2 secretion and binding Autocrine is a process whereby a cell secretes a chemical that acts upon itself, e.g. a helper T-cell secreting interleukin-2 that acts upon the same cell causing it to divide.

the process of secreting a hormone into the blood is classified as

endocrine

where are goblet cells located

epithelium of the conjunctiva

endometrial glands grow in number and length during which phase of the endometrial cycle

estrogenic

which structure connects the middle ear with the nasopharynx

eustachian tube

acidophils in the pars distalis of the adenohypophysis secrete

growth hormone GH

which is true regarding human breasts

modified apocrine sweat glands

which layer of the retina is closest to the vitreous body

optic nerve fiber layer

match the hormone with the secreting cell

parathormone: chief cell calcitonin: c cell glucagon: alpha cell glucocorticoid: zona fasiculata cell insulin: beta cell t3: thyroid follicular cell aldosterone: zona glomerulosa cell

the hypothalami-hypophyseal portal system begins in the capillaries of the hypothalamus and ends in capillaries in which of the following

pars distalis of the adenohypophysis

which structure of the ear is composed of epithelial tissue that contains blood vessel

stria vascularis

a primary oocyte is a female germ cell that is arrested in the first meiotic division of meiosis

true

at the time of ovulation a secondary oocyte arrested at metaphase in the second meiotic division is released

true

hormones are biological substances that act on specific target cells

true

multiple layers of ovarian follicular cells is called the stratum granulosum

true

parathyroid glands are composed of cells arranged in cords (strands) but the thyroid gland is composed of follicles that are lined with epithelial cells

true

parathyroid glands share their capsule with the thyroid gland capsule

true

process whereby a cell secretes a hormone that acts on cells nearby without entering the blood is known as paracrine secretion

true

spermiogenesis is the process of forming a sperm from a spermatid

true

the auditory tube is another name for the eustachian tube

true

the cortex of the ovary is where oocytes develop and are released by the process of ovulation

true

the ear canal is another term for the external auditory meatus

true

the epithelium of the epididymis is pseudo stratified with sterocilia

true

the parts of the adenohypophysis are pars tuberalis, pars intermedia, and pars tuberalis

true

when the ciliary muscle contracts the lens of the eye accommodates for focusing on objects close to the eye

true