Endocrine Glands
Describe the possible "other" functions of Oxytocin
A study shows oxytocin increases the "generosity" of people, but don't affect "altruism". Increases "cuddles", "social interactions", "empathy", "team sport camaraderie", "help protect monogamous relationships", "may increase aggressiveness", etc. No one knows its long-term consequences
Adenohypophysis: describe the 3 parts and the cells that make up them
*Note: chromophils take dye and stain whereas chromophobes do not (they look white)! 1. Pars tuberalis (Basophilic chromophils) -Gonadotropic: follicle-stimulating and luteinizing hormones (FSH + LH) 2. Pars intermedia (Basophilic chromophils (so can't tell the difference between these and cells of pars tuberalis)) -Melanotropic cells: produce POMC, which is cleaved into 2 forms of the melanocyte stimulating hormone 3. Pars distalis (3 types of cells) Basophilic chromophils: FSH, LH, ACTH, melanocyte SH, TSH: -Gonadotropic: produce follice-stimulating and luteinizing hormones -Corticotropic: produce corticotrophin and melanocyte stimulating hormone -Thyrotropic: produce thyrotropin Acidophilic chromophils: GH, prolactin -Somatotropic: produce growth hormone -Mammotropic: produce prolactin Chromophobes: -Stem and undifferentiated progenitor cells -Degranulated chromophilic cells
What is corpus arenaceum?
-Accumulations of concretions of calcium and magnesium - unknown function -Appear in childhood and start accumulating after puberty -They are used to located the pineal gland (condensed on an X-ray)
Embryology and description of adrenal glands?
-Adrenal glands (aka suprarenal glands) are derived from 2 different embryologic origins -They are paired organs that lie near the superior poles of the kidneys -Each gland is covered by a dense connective tissue capsule that sends septa into the interior of the gland as trabeculae -The gland has two layers: the cortex and the medulla, each with different origin, functions, and morphology
Describe Pancreatic islets of Langerhans
-Compact masses of endocrine tissue embedded within the acinar exocrine tissue of the pancreas -Derived embryologically from epithelial outgrowth from the endoderm (intestinal lining) near the bile duct -The islets are embedded within the acinar exocrine pancreatic tissue -A thin capsule of reticular fibers surrounds each islet and separates them from the surrounding aicinar tissue- -4 types of islet cells compose islets
Describe the Adrenal Cortex origin, contents, and zones
-Derives from the mesoderm -Contains cells that produce steroid hormones -The adrenal cortex has 3 concentric zones, each one producing a different class of hormones: 1. Zona glomerulosa - the external part, formed by closely packed, rounded or arched cords of columnar or pyramidal cells surrounded by capillaries. The cells in this region produce mineralocorticoids (aldosterone) 2. Zona fasciculata - consists of long cords of large polyhedral cells, separated by fenestrated sinusoidal capillaries. The cells in this region secrete glucocorticoids (cortisol) and small amounts of androgens 3. Zona reticularis - the innermost part of the cortex, in contact with the adrenal medulla -The cells in this region produce mainly dehydroepiandrosterone, a weak androgen that can be converted into testosterone in several tissues
Thyroid gland: Describe its components
-Each follicle consists of a simple epithelium surrounding a central lumen filled with colloid, which contains thyroglobulin, the precursor for the active thyroid hormones: thyroxine (or tetra-iodotyronine, T4), and tri-iodotyronine (T3). Parafollicular cells (C cells) , which produce calcitonin can be found within the follicular epithelium or as isolated clusters between follicles.
What are 2 types of secretion?
-Endocrine secretion -Exocrine secretion
Describe the diffuse neuro-endocrine system
-In addition to endocrine glands, many organs contain endocrine cells that produce hormones and have important endocrine functions -These glands are intercalated with the cells of organs including the heart, kidney, thymus, gut, and gonads -They produce hormones that can regulate the function of neighboring cells (paracrine) -The characteristics of these endocrine cells will be discussed in the lecture corresponding to each organ In this figure: Duodenum - cells produce gastrin, somatostatin, gastrin-cholecystokinin (present in granules); endocrine products released in capillaries, not the lumen
Describe the Adrenal Medulla origin and composition
-It derives from the neural crest -It is composed of chromaffin cells that can be considered modified postganglionic neurons (don't have axons or dendrites) -Chromaffin cells have electron-dense granules filled with epinephrine or norepinephrine -Epinephrine-producing cells locate near cortical sinusoids, whereas norepinephrine-producing cells locate near medullary arterioles
Origin of the Pineal gland?
-It develops with the brain from neuroectoderm in the roof of the diencephalon
Where is the thyroid gland located?
-Located in the cervical region anterior to the larynx
Pars distalis
-Most cells stain red and are eosinophilic -See some basophils and chromophobes -See capillaries with honeycomb structure
Where does thyroid gland originate?
-Originates from the foregut endoderm near the base of the future tongue The parenchyma is formed by rounded epithelial structures called thyroid follicles
Describe the hormones produce by the chief cells
-PTH is produced by the chief cells. Lowered extracellular calcium removes the calcium sensing receptor-dependent repression of PTH production. PTH is then free to mobilize the calcium from stores in the bone. PTH production may also be regulated by phosphate
Describe the Parathyroid gland
-Parathyroids are 4 small glands located in the back of the thyroid gland -Each parathyroid gland is contained within the capsule that sends septa into the gland, which is composed of 2 types of cells: the chief cells and the oxyphil cells.
Medical case history: Lionel Messi
-Proportional stature well below that expected for family heights -Below normal rate of growth -Delayed physical maturation -Delayed bone age -Low levels of IGF1, IGF2, IGF binding protein 3 -Diagnosed at age 11 of growth hormone deficiency -Received GH replacement andgrew to 5'6"
Based on their chemical structure, hormones can be classified as what?
-Proteins & glycoproteins -Small peptides -Amino acid derivatives -Steroids
Describe the chief cells and oxyphil cells
-The chief cells contain granules of parathyroid hormone (PTH) -The oxyphil cells (larger than chief cells, have acidophilic cytoplasm and abnormally-shaped mitochondria)
Describe the Hypothalamus" -Location? -Function?
-The hypothalamus is a small region located in the lower central part of the brain -It regulates the function of the pituitary and other organs -It contains the bodies of neurosecretory neurons, which produce the hormones that in turn control hormonal secretion by the pituitary gland -In addition, the supraoptic and paraventricular nuclei of the hypothalamus produce the hormones vasopressin (or antidiuretic hormone) and oxytocin, which acts in non-endocrine tissues (kidney and mammary glands/uterus, respectively)
Describe the Pineal gland
-The pineal gland is a small, pine-cone-shaped organ in the brain -It is located in the posterior of the 3rd ventricle and is covered by connective tissue. The most abundant secretory cells are the pinealocytes, which produce melatonin -It also contains interstitial glial cells, similar to astrocytes -It participates in the regulation of the daily rhythms of bodily acitivities (melatonin regulates the Circadian rhythm) -Involved in sensation, imagination, memory, and causation of bodily movements
Describe the pituitary gland or hypophysis
-The pituitary gland is an endocrine gland located below the brain in a cavity of the sphenoid bone, the sella turcica -Consists of 2 glands:the anterior adenohypophysis and the neurohypophysis. -The glands are united anatomically but have different functions
Describe the synthesis of thyroid hormones
-There are exocrine and endocrine components to synthesis of thyroid hormone -Thyroglbulin = inactive precursor -Transport of iodine from blood into the cell -crosses the basolateral membrane (2). Transfer of iodine to colloid (lumen-3). After thyroglobulin iodinated, it's incorporated back into the cell with some of the colloid by endocytic vesicles (5-6)
Origin of parathyroid gland?
-They derive from the pharyngeal pouches in the embryo (migrate to the developing thyroid in the embryo-although it might migrate to a different location)
What do pancreatic islets represent?
-They represent the second type of endocrine tissues - endocrine structure embedded in different organ
High levels of iodine have 2 implications. What are they?
1. A way to treat thyroid cancer is to give radioactive iodine = destruction of thyroid (since most iodine goes there) 2. If iodine deficient, can cause thyroid deficiency = reason why salt is iodized. Often happens if water is from river
Parts of the neurohypophysis?
1. Infundibular stalk (connects the neurohypophysis/posterior pituitary with thehypothalamus 2. Pars nervosa
What are the components of the endocrine system?
1. Major endocrine organs: the sole or major function of the organ is the synthesis, storage, and secretion of hormones 2. Endocrine components within other solid organs: clusters of endocrine cells within other tissues (ex. islet of Langerhans are endocrine in the pancreas) 3. Diffuse endocrine system: scattered individual hormone cells (or small clumps) usually within an extensive epithelium (ex. respiratory tract, gut, reproductive tissue)
Parts of the adenohypophysis?
1. Pars tuberalis - wraps around infundibular stalk 2. Pars intermedia - very thin 3. Pars distalis - largest part - makes up most of the anterior pituitary
Thyroid gland: The production, storage, and release of thyroid hormones involve a multistage process with both exocrine and endocrine functions. Describe these functions
1. Thyroglobulin (hormonally inactive) is synthesized in the RER and glycosylated in the RER and Golgi 2. Circulating iodine is incorporated through the basolateral cell membrane of the follicular cells 3. Iodine is transferred to the follicular lumen where is undergoes oxidation to active iodine 4. Tyrosine residues of thyroglobulin are iodinated in the lumen 5. Follicular cells take up colloid by endocytosis or pinocytosis. The endocytic vesicles fuse with lysosomes and move to the basolateral cell membrane while the thyroglobulin is degraded to render T3 and T4, which are then released to the circulation
Describe the types of cells that compose the Pancreatic islets of Langerhans
1. alpha cells - secrete primarily glucagon 2. beta cells - produce insulin and are the most abundant cell type 3. delta cells - secrete somatostatin and are less abundant than alpha and beta cells 4. F or pp cells secrete pancreatic polypeptide and are the less abundant cell type
Image of Adrenal gland
Adrenal glands are surrounded by a capsule. Adrenal medulla are where the veins are locted
Describe Oxytocin's role in metabolism of the body
Affects lipid metabolism, insulin production, glucose uptake, etc.
Where are the adenohypophysis and neurohypophysis developed?
Anterior pituitary (adenohypophysis) develops in the embryo from the oral ectoderm and the posterior neurohypophysis developed from the brain
What else does oxytocin effect?
Bone (osteoblast and osteoclasts) -Increases proliferation of osteoclasts (so more cells) BUT -Inhibits bone resorption so.....more osteoclasts but they don't work as well. Osteoblasts increase differentiation and proliferation
Slide of Adrenal medulla (zoomed in)
Can see purple chromaffin cells
Slide of Adrenal cortex
Capsule - formed by connective tissue ZG = round groups of cells ZF = columns of cells that are bigger/more columnar than ZG. All the columns and groups of cells are surrounded by capillaries
Describe Exocrine secretion
Compound released in apical membrane (opposite to BM) - can be merocrine, apocrine, or holocrine secretion
Pineal gland - what are the 2 types of cells?
2 types of cells: -Pinealocytes (produce hormone) -Astrocytes (glial cells, flattened nuclei, more darkly stained)
Describe Oxytocin
Oxytocin is said to be released at the time of delivery for smooth muscle contraction of the uterus AND stimulates the mammary gland to secrete milk. Over years, they found it had other functions.
Neurohypophysis
P: pituicytes NB: Herring bodies C: Capillaries
Adenohypophysis: know their location in the image
Pars distalis Pars tuberalis Pars intermedia
Neurohypophysis: Describe the Pars Nervosa and Infundibular stalk
Pars nervosa: -Expanded distal portion containing the neurosecretory axons of the hypothalamo-hypophyseal tract -The cell bodies of these fibers lie in the supraoptic and paraventricular nuclei of t hypothalamus -Hormones produced in the cell bodies are oxytocin and vasopressin -Hormones are stored in granules at the nerve terminal (Herring or neurosecretory bodies) -Oxytocin and vasopressin go through the axons to the pars nervosa where they are released at the nerve terminal (Herring/neurosecretory bodies) -The pars nervosa also contains fibroblasts, mast cells, and pituicytes Infundibular stalk (in the middle of neurohypophysis) -Neurosecretory nerve endings from hypothalamic neurons (other than supraoptic and paraventricular nuclei) -Hormones secreted in this region enter the hypothalamo-hypophyseal portal system and regulate the endocrine cells of the adenohypophysis
Describe the development of the adenohypophysis and neurohypophysis
Pituitary has dual embyonic origin. Forms part from floor of diencephalon (neuroectoderm) and part from roof of mouth (oral ectoderm) The 2 structures give rise to mature pituitary - both adenohypophysis - from Rathke's pouch (roof of mouth) and neurohypophysis from floor of diencephalon
What does thyroid gland produce?
Produces thyroxine (T4), tri-iodotyronine (T3), and calcitonin
Describe Endocrine secretion
Production of a compound across the basement membrane into blood vessels. Direct.
Slide: Follicular and parafollicular cells
S: septa C: capsule L: lumen F: follicular cells PF: parafollicular cells -Capsule sends Septa into parenchyma and separates the organ into lobules -In lumen, there is colloid, a gelatinous substance -Follicles are surrounded by flat cells - follicular cells that produce T3 and T4 -Between follicles are light-staining cells = parafollicular cells that produce calcitonin
Pars distalis slide
See capillaries - common for endocrine glands because they release the hormones into circulation. For pars distalis, these are sinusoids - capillaries with endothelial cells that are not in close connection with one another to allow passage of molecules through them
Hypophysis slide
Shows: Pars nervosa (light pink top middle/right) and Pars intermedia (blue) Note: the cells of the adenohypophysis have different staining (classified as chromophils (eosinophils/basophils) or chromophobes (don't take up any dye)
Describe the endocrine system
The endocrine system is a collection of glands that secrete hormones, molecules that transmit chemical messages. Hormones are released to the bloodstream and act on cells that express the appropriate receptor in target organs. Endocrine cells are typically composed of islands of secretory cells of epithelial origin that discharge their products into capillaries, unlike the cells of exocrine glands that release their products into an epithelial duct
Describe the Pituitary Portal System
The pituitary portal system, a special network of blood vessels, carries hormones from the hypothalamus to the anterior pituitary. The blood supply of the pituitary arises from 3 paired arteries originating from the internal carotid arteries. The superior hypophyseal arteries enter the medium eminence and form the external plexus close to the nerve endings from the neuroendocrine cells in the hypothalamus, which gives way to a parallel capillary network the runs down the pituitary stalk to form the long portal vessels. From the portal vessels run into the anterior pituitary. Additional blood supply to the posterior pituitary is derived from the small, middle, and inferior hypophyseal arteries
Describe the Vasculature of hypothalamus-hypophysis system
There is a tight relationship between the hypothalamus and pituitary due to regulated and extended blood flow from the hypothalamus to pituitary Vessels: 1. Primary capillary plexus: the superior hypophyseal arteries form a plexus of fenestrated capillaries that irrigate the median eminence 2. Long portal veins: run from the primary capillary plexus to the pars distalis -Neurosecretory cells of hypothalamus produce stimulatory and inhibitory hormones in dorsal and ventral media and infundibular nuclei - dump the hormones into these long portal veins which carry to pars distalis (so hormones are going all the way from the median eminence to the pars distalis) 3. Secondary capillary plexus: the capillaries of the primary plexus rejoin to form veins that elaborate a secondary capillary plexus 4. The hypophyseal portal system: transports neurohormones frmo the median eminence to the adenohypophysis (anterior pituitary) 5. The inferior hypophyseal system: Forms capillaries that provide blood primarily to the neurohypophysis 6. Short portal veins: links the pars nervosa with the pars distalis, the function of which is unclera 7. Superior and inferior hypophyseal arteries - both come off of internal carotid
Describe the Hypothalamus-hypophysis (pituitary) system
This is a tight relationship. There are 2 groups of neurons in the hypothalamus: 1. Neurons of supraoptic and paraventricular nuclei - long axons go all the way down to the neurohypophysis area of the posterior pituitary. The hormones produced here are stored and released to circulation when necessary. 2. Neurons of the dorsal medial, ventral medial, and infundibular nuclei - produce hormones that regulate function of pituitary. Products released into blood stream and affect endocrine cells in adenohypophysis of anterior pituitary. Have short axons.
Slide of Adrenal cortex
Zona reticularis - usually stains very dark; organized group of cells; have inclusions of lipofuscin
What are endocrine glands?
Endocrine glands are specialized organs that produce, store, and secrete hormones into the blood stream. Hormones released directly through circulation. Endocrine glands usually formed by modified epithelial cells with a secretory capacity.
Slide of Adrenal medulla
Formed by chromaffin cells - purple staining cells. The pinker cells on the left are sympathetic neurons in the medulla
Glucagon and insulin are regulated by ____?
Glucagon and insulin are regulated by circulating levels of glucose
What are the hypothalamic hormones?
Hormones are produced by neurons. Hormones that are produced by dorsal medial, ventral medial, and infundibular nuclei are the first 6 (some stimulate and some inhibit the release of hormones) Vasopressin and oxytocin are released to circulation by the posterior pituitary - these affect mammary glands, uterus, and kidney.
Islet of Langerhans image
Islet of Langerhans: The insulin-secreting beta cells (green) normally exhibit a perinuclera cap of proinsulin (orange) -Nuclei are blue -Ones that aren't green or orange are alpha, delta, or F cells
Slide: Follicular and parafollicular cells
Left: See follicular cells - flat cells that line the lumen. Parafollicular cells usually not in contact with the lumen. Both are located within the basement membrane that separates the cells from the capillaries. Capillaries are the white areas (the one on the left with a C shape inside it) Right: Parafollicular cell with lots of granules that contain calcitonin
