Ch. 16-Endocrine System

Adrenocorticotropic Hormone

(ACTH) of the anterior pituitary. (tropic hormone) Target- Adrenal cortex Effects- Growth of adrenal cortex, secretion of glucocorticoids. Regulates the endocrine activity of the cortex portion of the adrenal gland. Type -Non-steroidal peptide

Antidiuretic Hormone

(ADH) of the posterior pituitary. Target- Kidneys Action- Water retention Type- Non-steroidal peptide

Mineralcorticoids

(ALDOSTERONE) of the adrenal cortex Target- Kidney Action- Promotes Na and water retention and K excretion; maintains blood pressure and volume Type- steroid

Oyphil Cells of the parathyroid

The function of the scattered much larger oxyphil cells is unknown

Hypersecretion of thyroxine (T4)

causes elevated metabolic rate, nervousness, weight loss, sweating, and irregular heartbeat.

Atrial Natriuretic peptide

(ANP) of the heart Target- Kidney Action- Lower blood volume and pressure by promoting Na and water loss. Type- non-steroidal peptide

Glucocorticoids

(CORTISOL, CORTISONE and CORTICOSTERONE) of the adrenal cortex Target- Most tissues Action- Stimulates fat and protein catabolism, gluconeogenesis, stress resistance, and tissue repair Enables the body to resist long-term stressors, primarily by increasing blood glucose levels. Type- Steroid

Parafollicular cells

(c cells) The thyroid gland also contains nests of c (clear) cells, or parafollicular cells, at the periphery of the follicles. They respond to rising levels of blood calcium by secreting the hormone calcitonin. Calcitonin antagonizes parathyroid hormone and stimulates osteoblast activity, thus promoting calcium deposition and bone formation. It is important mainly in children, having relatively little effect in adults.

Sex hormones (gonadocorticoids)

(cheifly ANDROGENS(dehydroepiandrosterone (DHEA) of the adrenal cortex Target- Bone, muscle, integument, brain, and many other tissues. Action- Precusor of testosterone; indirectly promotes growth of bones, pubic and axillary hair, apocrine glands, and fetal male reproductive tract; stimulates libido Type- steroid

Pancreatic Islets

(islets of Langerhans) contains approx. 20% alpha cells and 80% beta cells. Alpha cells secrete glucogon when blood glucose falls below 100mg/dL. Beta cells secrete insulin during and immediately following a meal when blood nutrient levels are rising.

Hypothalamus

8 hormones produced by the hypothalamus.There are six hormones to regulate the anterior pituitary and two that are stored in the posterior pituitary and released on demand. The first six are described as releasing hormones if they stimulate pituitary cells to secrete hormones of their own, or inhibiting hormones if they suppress pituitary secretion. The other two hypothalamic hormones are oxytocin and antidiuretic hormone

Acinar cells of the pancreas

Form the major portion of the pancreatic tissue. Acinar cells produce the exocrine secretion of hydrolytic enzymes that is released into the duodenum through the pancreatic duct. Alkaline fluid produced by duct cells accompanies the hydrolytic enzymes.

Diabetes insipidus

Hyposecretion of ADH results in dehydration from excessive urine output, a condition called diabetes insipidus. Individuals with this condition experience an insatiable thirst.

infundibulum and sella turcica

Pituitary gland (Hypophysis) is suspended from the floor of the hypothalamus by a stalk (infundibulum) and housed in a depression of the sphenoid bone, the sella turcica.

Pituicytes of the posterior pituitary

Posterior pituitary is where two hormones (oxytocin, and anti-diuretic hormone) synthesized by the hypothalmic neurons are stored. Observe the axons of the hypothalamic neurons that compose most of this portion of the pituitary. Also note the glial cells or pituicytes.

Zona fasciculata of the adrenal cortex

The deeper intermediate zona fasciculata produces glucocorticoids. This is the thickest part of the cortex. Its cells are arranged in parallel cords.

Zona reticularis of the adrenal cortex

The innermost cortical zone the zona reticularis produces sex hormones and some glucocorticoids. The cells here stain intensely and form a branching network.

Hypothalamic-hypophyseal tract

The neurohypophysis is actually nervous tissue (nerve fibers and neuroglia) not a true gland. Nerve fibers arise from certain cell bodies in the hypothalamus, pass down the stalk as a bundle called the hypothalmo-hypophyseal tract.

Zona Glomerulosa of the adrenal cortex

The outermost zona glomerulosa where most mineralcorticoid production occurs, the tightly packed cells are arranged in spherical clusters

Pancreas

The pancreas located partially behind the stomach in the abdomen, functions as both an endocrine and exocrine gland. It produces digestive enzymes as well as insulin and glucagon, important hormones concerned with the regulation of blood sugar levels.

Thyroid gland follicles, follicular cells and thyroglobulin

The thyroid is composed mostly of sacs called thyroid follicles. Each is filled with a protein rich colloid called thyroglobulin and lined by a simple cuboidal epithelium of follicular cells. These cells secrete mainly the hormone thyroxine, also known as T4 because of its four iodine atoms. It also produces triiodothyronine (T3) with three iodine atoms.

Chromophobes of the anterior pituitary

do not take up stain. appear dull and colorless. The role of chromophobes is controversial, but they apparently are not directly involved in hormone production.

Parathyroid glands

found embedded in the posterior surface of the thyroid gland. Usually there are four of them, partially embedded in the posterior surface of the thyroid. Often however they occur in other locations ranging from as high as the hyoid bone to as low as the aortic arch. About 5% of people have more than four parathyroids. They secrete parathyroid hormone, the most important regulator of calcium balance of the blood.

Hyposecretion of PTH

increases neural excitability and may lead to tetany, prolonged muscle spasms that can result in respiratory paralysis and death.

Tropic Hormone

stimulates its target organ, which is also an endocrine gland, to secrete its hormones. Target organ homones then exert their effects on other body organ and tissues. The anterior pituitary tropic hormones include Gonadotropins- follicle stimulating hormone (FSH), and luteinizing hormone (LH). And Adrenocorticotropic hormone (ACTH), Thyroid-stimulating hormone (TSH).

Follicle Stimulating Hormone

(FSH) of the anterior pituitary. (tropic hormone) Target the ovaries and testes Effects (F) growth of ovarian follicles and secretion of estrogen (M) sperm production Type- Non-steroidal peptide

Growth hormone

(GH) of the anterior pituitary Target- liver, bone, cartilage, muscle, fat (entire body) Action- Widespread tissue growth, especially in the stated tissues Type- Non-steroidal peptide

Growth hormone plays an important role

(GH) plays an important role in determining body size. It affects many tissues of the body; however, its major effects are exerted on teh growth of muscle and the long bones of the body. Hyposecretion results in pituitary dwarfism in children. Hypersecrection causes gigantism in children and acromegaly (overgrowth of bones in hands, feet, and face) in adults.

Pituitary Gland

(Hypophysis) is suspended from the floor of the hypothalamus by a stalk (infundibulum) and housed in a depression of the sphenoid bone, the sella turcica. It consists largely of two functional lobes, the adenohypophysis, or anterior pituitary and the neurohypopysis consisting mainly of the posterior pituitary.

Luteinizing hormone

(LH) of the anterior pituitary. (tropic hormone) Target- ovaries and testes Effects (F) ovulation, maintenance of corpus luteum (M) testosterone secretion Type- Non-steroidal peptide

Oxytocin

(OT)of the posterior pituitary. Target- Uterus and mammary glands Action- Labor contractions, milk release; possibly involved in ejaculation, sperm transport, sexual affection, and mother-infant bonding. Type- Non-steroidal peptide

Prolactin

(PRL) of the anterior pituitary. Target- Mammary glands, testes Action- (F) milk synthesis (M) increased LH sensitivity Type- non-steroidal peptide

Parathyroid hormone

(PTH) of the parathyroid gland. Target- Bone, kidneys, small intestine Action- Raises blood Ca level by stimulating bone resorption (osteoclasts) and inhibiting deposition (osteoblasts), and enhancing calcitrol synthesis. Type- Non-steroidal peptide

Thyroid hormone (T3 and T4)

(TH) of the thyroid gland. Target- Most body tissues Action- Elevate metabolic rate and heat production; increase RR, HR, and strength of heartbeat; stimulate appetite and accelerate breakdown of nutrients; promote alertness and quicken reflexes; stimulate growth hormone secretion and growth of skin, hair, nails, teeth, and fetal nervous system Type- Non-steroidal amino acid

Thyroid - stimulating hormone

(TSH) of the anterior pituitary (tropic hormone) Target- Thyroid gland Effects- Growth of thyroid, secretion of thyroid hormone Type- Non-steroidal peptide

Hypophyseal portal system

The anterior pituitary controls the activity of so many other endocrine glands that it has often been called the master endocrine gland. However, the anterior pituitary is controlled by neurosecretions, releasing or inhibiting hormones, produced by neurons of the ventral hypothalamus. These hypothalamic hormones are liberated into teh hypophyseal portal system and carried to cells of the anterior pituitary where they control release of anterior pituitary hormones.

hypophyseal portal system

The anterior pituitary has no nervous connection to the hypothalamus but is linked to it by a complex of blood vessels call the hypophyseal portal system. This system consists of a network of primary capillaries in the hypothalamus, a group of small veins called portal venules that travel down the stalk, and a complex of secondary capillaries in the anterior pituitary. The hypothalamus controls the anterior pituitary by secreting hormones that enter this portal system.

Adrenal Glands

Two adrenal glands are located atop or close to the kidneys. Anatomically, the adrenal medulla develops from neural crest tissue, and it is directly controlled by the sympathetic nervous system. The medullary cells respond to this stimulation by releasing epinephrine (80%) or norepinephrine (20%), which act in conjuntion with the sympathetic nervous system to elicit the fight or flight response to stressors.

Thymus

is a gland situated in the superior thorax, posterior to the sternum and anterior to the heart and lungs. Conspicuous in the infant, it begins to atrophy at puberty, and by old age it is relatively inconspicuous. The thymus produces several different families of hormones including thymulin, thymosins, and thymopoietins. These hormones are thought to be involved in the development of T lumphocytes and the immune response.

Thyroid gland

is composed of two lobes joined by a central mass, or isthmus. It is located in the throat, just inferior to the larynx. It produces two major hormones, thyroid hormone and calcitonin.

Hyposecretion of thyroxine (T4)

leads to a condition of mental and physical sluggishness, which is called myxedema in the adult

Epinephrine, norepinephrine, and dopamine

of the adrenal medulla Target- Most tissues Action- Promotes alertness; mobilize organic fuels; raise metabolic rate; stimulate circulation and respiration; increase blood glucose level; inhibit insulin secretion and glucose uptake by insulin-dependent organs (sparing glucose for brain) Type- Non-steroidal amino acid

Insulin

of the pancreatic islets Target- most tissues Action- stimulates glucose ad amino acid uptake; lowers blood glucose level; promotes glycogen, fat, and protein synthesis Type- Non-steroidal peptide

Glucagon

of the pancreatic islets Target- mostly liver Action- stimulates amino acid absorption, gluconeogenesis, glycogen and fat breakdown; raises blood glucose and fatty acid levels Type- Non-steroidal peptide

Melatonin

of the pineal gland. Target-Brain Action-uncertain; may influence mood and sexual maturation. Exhibits a diurnal (daily) cycle. It peaks at night, making us drowsy, and is lowest around noon. Type-Non-steroidal amino acid

Calcitonin

of the thyroid gland. Target- Bone Action- stimulates bone deposition, mainly in children Type- Non-steroidal peptide

Adenohypophysis

or anterior pituitary secretes a number of hormones. Four tropic hormones- follicle-stimulating hormone(FSH), luteinizing hormone (LH), adrenocorticotropic hormone (ACTH), and thyroid stimulating hormone (TSH). Two other important hormones produced by the anterior pituitary are - growth hormone (GH) and prolactin (PRL).

Neurohypophysis

or posterior pituitary. is not an endocrine gland in a strict sense because it does not synthesize the hormones it releases. Instead, it acts as a storage area for two hormones transported to it via the axons of neurons in the hypothalamus. The hormones are released in response to nerve impulses from these neurons. The hormones stored in the posterior pituitary are oxytocin and anti-diuretic hormone

The Adrenal Cortex

produces three major groups of steroid hormones, collectively called corticosteroids. Mineralocorticoids (aldosterone). Glucocorticoids (cortisol (hydrocortisone), cortisone, and corticosterone). Gonadocorticoids (chiefly adrogens/male sex hormones)(but some estrogens/female sex hormones)

acidophil cells of the anterior pituitary

reddish brown cells which produce growth hormone and prolactin

Hypersecretion of ADH

results in adema, headache and disorientation

Hyposecretion of ADH

results in dehydration from excessive urine output, a condition called diabetes insipidus. Individuals with this condition experience an insatiable thirst.

Hypersecretion of PTH

results in loss of calcium from bone, causing deformation, softening, and spontaneous fractures.

Medulla

secretes epinephrine and norepinephrine

Pineal gland

small cone-shaped gland located in the roof of the third ventricle of the brain. Its major endocrine product is melatonin.

Cheif cells of the parathyroid

synthesize parathyroid hormone are small and abundant and arranged in thick branching cords

The pituitary gland consists largely of

the adenohypophysis, or anterior pituitary and the neurohypopysis consisting mainly of the posterior pituitary

basophil cells of the anterior pituitary

whose deep blue granules are responsible for the production of the tropic hormones (TSH, ACTH, FSH, and LH)