Flashcards in Unit 6 - Endocrine Glands Deck (32)
what are mechanisms of hormone actions?
1. membrane-impermeable (hydrophilic)
-receptors located on cell surface (don't enter cell)
-act via secondary messengers
-ex: peptides, PRO, glycoPRO, modified AA
2. membrane-permeable (hydophobic)
-intracellular receptors are DNA-binding PRO that affect transcription
-ex: steroid, TH
what are typical features of cells producing PRO hormones?
-hormones often stored in secretory granules
what are typical features of cells producing steroid normones?
-lipid droplets in cytoplasm
-abundant SER for cholesterol synthesis
-spherical mitochondria with characteristic tubular/vesicular cristae
structure of anterior pituitary
derived from oral ectoderm
-consists of epithelial tissue = adenohypophysis
3 regions are pars tuberalis, pars distalis, and pars intermedia
structure of posterior pituitary
derived from neural ectoderm
-consists of neurons and glia = neurohypophysis
2 regions arei nfundibular stalk and pars nervosa
how are cells in anterior pituitary divided?
1. chromophils - basophils and acidophils
2. chromophobes - stem/progenitor cells, cells that released granules, or lost granules during fixing
what are acidophils in anterior pituitary?
produce 2 types of PRO hormones
what are basophils in anterior pituitary?
glycoPRO hormones: FSH, LH, TSH
small polypeptides: ACTH, beta-LPH (lipotropin)
what are the percentages of secretory cells in anterior lobe? the hormone secreted? its role?
somatotrope: 50% - GH - growth of long bones
lactotrope: 15-20% - PRL - stimulate milk secretion
gonadotrope: 10% - FSH and LH - regulate ovarian follicle development, spermatogenesis, estrogen, and androgen secretion
thyrotrope: 5% - TSH - regulate TH secretion
corticotrope: 15-20% - ACTH - stimulate adrenal cortex hormone secretion
-also lipotropin - promotes utilization of fat
first 2 are acidophilic, last 3 are basophilic
in what parts of the anterior pituitary are hormones produced?
pars distalis and pars tuberalis
-the pars intermedia is largely inactive in adults, and has colloid-filled follicles and (Rathke's) cysts of unknown function
what kinds of cells does the neurohypophysis have?
axons and glial cells (pituicytes)
-has NO secretory cells
-cell bodies of neurons are in hypothalamus
-hormones are stored in dilated axons
--eosinophilic dilations are called Herring bodies
structure and origin of adrenal glands?
have outer layer (cortex) and inner layer (medulla)
-cortex has epithelial origin and 3 concentric zones: zona glomerulosa outer - zona fasciculata - zona reticularis inner)
-medulla has neuronal origin
what kinds of cells are in the adrenal cortex?
typical features of steroid-producing cells; usually have foamy appearance = foam cells
-acidophilic cytoplasm with lipid droplets
-abundant SER for cholesterol synthesis
-spherical mitochondria with characteristic tubular cristae contain enzymes involved in synthesis of steroid hormones from cholesterol
what kinds of cells are in the adrenal medulla?
cells have electron-dense secretory granules that react with chromium and silver salts (so called chromaffin or argentaffin)
-make catecholamines (epinephrine and norepinephrine)
what hormones are made by the adrenal cortex, and where?
zona glomerulosa: mineralcorticoids (mostly aldosterone to regulate salt balance)
-regulated by angiotensin II
zona fasciculata: glucocorticoids (mostly cortisol), some DHEA (regulate glucose metabolism)
-regulated by ACTH
zona reticularis: cortisol and weak androgen DHEA (glucose regulation and testosterone production)
-regulated by ACTH
what hormones are made by the adrenal medulla, and where?
all of medulla makes catecholamines (E/NE) for fight-or-flight response
-regulated by SNS
what happens to the adrenal cortex if the pituitary is removed, or there is a tumor?
no hypophysis: cortex gets smaller, medulla stays the same
tumor: cortex gets larger, medulla stays the same
adrenal cortex hyperactivity
-excessive cortisol causes weight gain, central obesity, hyperglycemia, easy bruising
--adrenal adenoma: 10%
--adrenal carcinoma: 5%
--other causes: 5%
--pituitary adenoma: 70%
--ectopic ACTH secretion by a tumor: 10%
islets of Langerhans
compact masses of endocrine tissues embedded w/in exocrine tissue of pancreas
-polygonal/round cells arranged in cords
-typically PRO-secreting cells (abundant RER, golgi)
-lightly stained (lighter than exocrine tissue)
-cells have secretory granules
-make polypeptide hormones
what is the quantity of cell types in islets of Langerhans?
alpha: 20% - in periphery - make glucagon
beta: 70% - centrally located - make insulin
delta: 5-10% - make somatostatin to inhibit other islet hormones, inhibit GH, TSH, and HCl secretion
F or PP: very rare - make pancreatic polypeptide to stimulate gastric chief cells but inhibit bile and pancreatic enzyme secretion
where is the thyroid and structure?
anterior to trachea
-has follicles, spherical structures lined by simple epithelium and filled with colloid
-colloid has storage form of TH called thyroglobulin
what do thyroid follicular cells look like and do?
vary in shape from cuboidal to low columnar
-have features characteristic of PRO-secreting cells (abundant RER and golgi)
-activity regulated by TSH made in anterior pituitary
-T3/4 regulate basal metabolic rate, body growth/development, and heat production
what do parafollicular cells (C-cells) look like and do?
larger in size than follicular cells
-appear pale in H&E prep
-located in basal lamina of follicles or between follicles
-make calcitonin that inhibits bone resorption and promotes calcification of bone (opposite of PTH)
-regulated by blood Ca++ levels
there are parathyroid glands? what kind of cells do they have?
4 small oval glands on the back of the thyroid
-chief cells - make PTH
-oxyphil cells - no known function
what do parathyroid gland chief cells do?
abundant small polygonal cells that are pale staining, and slightly acidophilic cytoplasm
-make PTH (polypeptide) that increase blood Ca++ level by regulating osteoclast activity, kidney excretion of Ca++, vit D synthesis, and intestinal absorption of Ca++
-regulated by Ca++ level in blood
what do oxyphil cells of parathyroid gland do?
large cells that are highly acidophilic (thus oxyphilic)
-less abundant than chief cells
-unknown function, but may make some PTH
what are some hormones secreted by non-endocrine hormones?
heart - ANP
kidney - erythropoietin, reinin
stomach/SI - enteric hormones
adipose tissue - leptin, adiponectin, steroid hormones
what does ANP do?
in heart; regulates BP and electrolyte balance
what do adipose hormones do?
leptin: regulate appetite and metabolism
adiponectin: regulate FA and glucose metabolism, and modulates sensitivity to insulin