Endocrine Flashcards
intro+types of secretions
secretory cells of endocrine cells secrete hormone to nearby vascularized compartment for distribution
- NO SECRETORY DUCT
- endocrine cells epithelial which aggregate as CORDS/clusters
- NT are HYDROPHILIC: proteins, phospholipids, and peptides
- thyroid hormones+steroid: HYDROPHOBIC, must circulate on transport mol + diffuse through cell + activate cytoplasmic receptors on target
1) PARACRINE secretions: secrete for close targets through interstitial fluid, short loops of blood vessels
- gastrin (pyloric G cells) -> fundus glands
2) JUXTACRINE secretions: has signalling mol (ligands), binds to receptor and diffuse inside cell (when in contact)
- F:embryonic+regeneration
3) AUTOCRINE- secrete mol that act on themselves or similar cells
- F: IGF insulin-like factor acts on same cell that secretes
pituitary and embryo
short summary
blood supply
pituitary- 0.5g, on sphenoid bone sella turcica covered by diaphragms sellae
- from brain (neurohypophysis) and developing oral cavity (adenohypophysis)
brain: NEUROHYPOPHYSEAL BUD grows down from the floor of future diencephalon as a stalk=infundibulum
mouth cavity: outpocket of endoderm, from roof of primitive mouth cranially forms RATKE’S pouch (hypophyseal pouch). base of pouch constricts+ separates pharynx (merge w neurohypophyseal bud). anterior wall thickens, reduce pouch lumen to fissure. small extension of pouch cells grows along stalk =pars tuberalis
pituitary gland divides into adenohypophysis (ant pituitary): pars distalis (anterior lobe; chromophils-acidophils: somatotrophs+ lactotrophs+ gonadotrophs and basophils: thyrotrophs+corticotrophs) + pars tuberalis (mostly gonadotrophs)+ pars intermediate (chromophobes-stain weakly, **degranulated, stem cell and undifferentiated projenitor cells) ** neurohypophysis (post pituitary)
- blood supply from internal carotid a. inferior hypophyseal a (supplies neurohypophysis) superior hypophyseal a (infundibular stalk+ medial eminence) branches and forms primary capillary plexus. then rejoin form venules of secondary capillary plexus in adenohypophysis
F: transport neuropepetides from hypothalamus to adenohypophysis to inhibit/release hormones
adenohypophysis+ regulation
pars distalis - 75%, thin fibrous capsule, CORDS of well-stained endocrine cells interspersed w fenestrated capillaries supported by RETICULAR fibres. TRABECULAE epi and fibroblast. has CHROMOPHILS: secretory cells where hormone’s stored in cytoplasmic granules.
- acidophilic
1) SOMATOTROPHS- 50% (most abundant) Growth hormone; stimulate epiphyseal plates via IGF in liver
2) LACTOTROPHS- 15-20% for prolactin, milk secretion
3) GONADOTROPHS- 10%, FSH (promote ovarian follicle, increase estrogen and spermatogenesis. LH- promote ovarian follicle maturation+pregestorone secretion+ interstitial cell androgen secretion in men. ICSH interstitial cell stimulating hormone (testosterone?)
- basophils
1) THYROTROPHS: least abundant 5%, stimulate thyroid synthesis, storage and liberation
2) CORTICOTROPHS main proteins POMC (pro-opiomelanocytes) cleaved-> ACTH and B-LPH (beta-lipoprotein)
pars tuberalis- smaller funnel shaped region w infundibulum of neurohypophysis. has most GONADOTROPHS
pars intermedialis
narrow zone between pars distalis and pars nervosa. CHROMATOPHOBES, small colloid cysts from lumen of ratkes pouch. BASOPHILS: corticotrophs expresses POMC which cleaves it - gamma-LPH (lipotrophin) and beta-endorphin
reg ant pituitary
- peptide related hypothalamic hormones (by small neurons in third ventricle, discharged by axons in median eminence, and transported by capillaries of portal system. the hypothalamic releasing hormones/ inhibiting neurons carried via primary capillary plexus->venules forming secondary in adenohypophysis via hypophysis portal system -> hormone bind to receptor to inhibit or excite/release.
due to position of hypothalamic neurons sensory stimuli and from CNS can affect pituitary function - negative feedback by hormones of target organs after hypothalamic factors and by hormones secreted by pituitary cells: hormone reaches threshold and hypothalamus releases inhibiting hormone and ant pituitary stops releasing hormone
- hormone secretin of anterior pituitary affected by other hormones: ghrelin from mucosa of stomach affects secretion of somatotrophin +oxytoxin released during breast feeding (increase prolactin)
neurohypophysis
pars nervosa+infundibulum (stalk+ medial eminence)
NO TRABECULAE epi
100,000 unmyelinated axons have cell bodies in supraorbital (ADH) and supraventricular nuclei (oxytocin- both are 9 amino-peptide hormone)
hormone transported by axon in pars nervosa-> accumated axonal dilations = HERRING BODIES/neurosecretory bodies
herring bodies: slightly EOSINOPHILIC, have MEMBRANE-BOUND granules w the 2 hormones bound to NEUROHYPOPHYSIS I II. (cleaved to peptide hormones+ protein carrier). AP stimulated in supraoptic+supraventricular nuclei-> stimulate release of hormones->distributed by fenestrated capillaries (INFERIOR HYPOPHYSEAL a)
ADH antidirectic h- OSMORECEPTORS in hypothalamus sense change in tonicity (osmotic pressure). F: maintain hormone level (increase tonicity ADH released causes permeability of collecting duct and to h20-more reabsorbed to restore osmotic balance)
Oxytosin- contraction of uterine smooth m+myoepithelial cells in mammary glands. nursing infant induce oxy by stimulating secretory tract acting on hypothalamus in neurohormonal reflex
adrenal gland
- superior region of kidney, embedded in adipose tissue+ fascia
- flattened, half moon shaped 8g, 4-6cm, 1-2cm, 4-6 thick
- glands covered dense CT capsule send THIN TRABECULAE to gland’s parenchyma
- stroma: RETICULAR fibres (support microvasc+secretory cells) , 2 regions: cortex (mesoderm) and medulla (neural crest).
- capillary irrigate endocrine cells in cortex and then sends -> medulla
cortex: slightly ACIDOPYHILIC due to LIPID DROPLETS W CENTRAL NUCLEI ; secrete STEROID (SER produce cholesterol, mitochondria, both convert prohormone ->active steroid). secrete epi+norepi which diffuse freely, no granules +no exocytosis
zona glomerulosa: 15%, closely packed HORSESHOE/round/arched CORDS in pyramidal/ COLUMNAR cells w capillaries. slightly BASOPHILIC/CLEAR cyto. Produces MINERALOCORTICOIDS = aldosterone (high Na permeability). stimulated by ANGIOTENSIN II+ high K+. some weak stimulation by ACTH.
zona fasciculata 65-80%, LONG CORDS w large polyhedral cells 1 or 2 cell thick+divided by sinusoidal capillaries. abundant lipid droplet+appear vaculated. SPONGIOCYTES: STEROID secreting (ser+mito w tubular cristae) GLUCOCORTICOID- secrete corticoid+corticosteroid= stimulate carb+glycogen and activate gluconeogenesis in liver. controlled by ACTH w (-) feedback proportional to circulating glucocorticoid. WEAK ANDROGEN also produced (DHEA dehydroepiandrosterone)
Zona reticularis-10% innermost, smaller cells in network IRREG CORDS w capillaries. heavily stained bc lipofuscin pigment> lipid droplet. JUXTAMEDULLARY layer- slightly EOSINOPHILIC cyto + lipid granules. produced primarily WEAK ANDROGEN: DHEA dehydroepiandrosterone (converts to testosterone); controlled by ACTH.
Medulla: large pale staining POLYHEDRAL cells in cords/clumps. supported by RETICULAR fibres. has capillaries and PARASYMPATHETIC ganglionic cells. CHROMAFFIN (medullary parenchymal cells): modified sympathetic postganglionic fibres. OVOID CLUSTERS, well develop GA, secretory granules. converts norepi->epi. innervated by sympathetic preganglionic fibres during stress. medulla has e- dense secretory granules which CATECHOLAMINES= epi (less e- dense) +norepi. both catecholamines+ATP+Ca2+ bind to granular storage=CHROMAGRANIN.
- epinephrine: large dense core vesicles: dilate bronchiole, arteries of cardiac+sk muscle, increase heart rate.
- norepinephrine smaller OSMIOPHILIC granules. some found in paraganglia. constriction bronchiole, vessels of digestive system+skin. blood flow TO heart increased.
- both stimulate glycogen breakdown (glucose)+ fight/flight+ normal activity still secrete small amounts
islets of langerham
- compact+ spherical/oval masses of endocrine cells. embedded in ACINAR exocrine tissue. Which is separated from islet by thin RETICULAR capsule
- both have same embryonic dev: epithelial outgrowth of endoderm of developing gut - 100-200um =d around 1 million islets, most on TAIL of pancreas
- islets are polygonal/ROUNDED +smaller+lightly stained compared to acinar cells. arranged in cords+ FENESTRATED capillaries
- HE and trichrome stains islet as acido/basophilic w fine cytoplasmic granules. ultrastructural features: active polypeptide- secreting cells w secretory granules
A: 20% glucagon, peripheral
B: 80%, insulin, centrally
D: somatostatin, less abundant and scattered
Function: inhibit secretion of other: GH+thyroid hormone, HCL. also released by hypothalamus called GHIH
F or PP: pancreatic polypeptide, conc on head of pancreas
function: stimulate cystic chief cells; inhibit: bile secretion, pancreatic enzyme+bicarbonate, intestinal motility
70mg/dL glucose
islets have enterochromaffin cells (DNES) : secrete polypeptides for digestive system; 10% affect a,b,d
- parasympathetic n (both)+ sympathetic n (increase glucagon+ insulin) nerve ending associated w secretion
- neural stimulus pass through gap j
type 1: juvenile, insulin dep, partial/total autoimmune def of b cells
type 2: later in life, failure of cells to resp to insulin. assoc to obesity
DNES
diffuse neuroendocrine cell system
origin: endoderm of embryonic gut+bronchial buds
location: bronchopulmonary tract, islets of L (in enterochromaffin cells on both sides of islet +small duct of pancreas)
F: produces polypeptides+ NT (seratonin+ 5hydroxytruptamine= called APUD cells)+ reg motility and secretion in digestive tract
stain: CHROMIUM SALT= ENTEROCHROMAFIN cells
SILVER NITRATE= ARGENTAFFIN cells
immunohistochemistry: antibody against (insulin- stains b cell)
thyroid gland
reg
production
location: anteroinferior to larynx
butterfly-shaped gland w 2 lobes divided by isthmus
embryo: foregut ENDODERM near base of tongue
fibrous capsule septa extend to parenchyma dividing into lobules carrying blood vessels, nerves, lymphatics
stroma in capsule well vasc w FENESTRATED capillaries for transportation of hormone
F: thyroid hormone production, T4 thyroxine+T3 tri-iodothyronine. growth+cell differentiation, basal metabolism (w help of calcitonin)-lipid+protein + carb metabolism , O2 consumption.
parenchyma: millions of rounded thyroid FOLLICLES w simple CUBOIDAL/COLUMNAR epi w central lumen +densely filled w gelatinous ACIDOPHILIC COLLOID (has THYROGLOBULIN-precursor of active thyroid+storage of inactive thyroid). large amount product stored.
follicular cell/THYROCYTES
on BASAL lamina:
- SIMPLE SQ cells (hypoactive) OR SIMPLE COLUMNAR cells (active) w round nucleus centrally located
-basally has RER; apically rich GA, secretory granules colloidal material, PHAGOCYTES, MICROVILLI, LYSOSOMES AND JUNCTIONS
- densely packed w THIN RETICULAR tissue between
F: active protein synthesis+ secretion, phagocytosis+digestion
- controlled by TSH w abundant receptors on basal membrane of thyrocytes
PARAFOLLICULAR cells (C cells)
- neural crest derived
- basal lamina has follicular epi or isolated clustered between foramen
- bigger, less intensely stained, less RER. large GA, small = granules (100-180um) produce CALCITONIN. (triggered w high Ca, inhibit osteoclast)
reg by TSH- by RECEPTORS on basal cm of thyrocytes. increases cell height in follicular epithelium+stimulate production and release of thyroid hormone but inhibit release of TSH (NEGATIVE FEEDBACK) to maintain T3+T4. increase TSH in cold, decreases in hot +stress
production: TSH increases # and soze of mito+protein synthesis to enhance metabolic activity
1) production w THYROGLOBULIN
synthesis rer+ glycosylation in GA; 140 THYROSIL RESIDUES, apical vessels in thyrocytes lumen contain glycoprotein;
2) uptake of I
Na/I symporters NIS in thyrocytes basolateral cm (allow 30 fold conc of dietary Iodide in thyroid tissue)
pendrin: I/Cl apical transporter pumps I from thyrocytes into colloid
3) IODINATION of tyrosyl residues (AA residue w tyrosine) in thyroglobulin
oxidation of I-> membrane-bound thyroid peroxidase of microvilli of thyrocytes
cause iodination of 1 or more atoms in colloid
4) forms T3+T4
2 iodinated tyrosines=part of colloidal thyroglobulin
covalently conjugated in coupling reactions
5) ENDOCYTOSIS of iodinated thyroglobulin
by thyrocytes: pinocytosis+ receptor-mediated endocytosis
fuses w lysosomes, thyroglobulin degraded by lysosome protease and free active T3 T4
6) SECRETION of T3+T4 endocrine manner to basolat domain of thyrocytes, both bind to thyroxine-binding globulin/albumin
T4 abundant, both bind to intracellular receptors of target cells.
T3 is 2x to 10x more active >T4
half life T3=1.5d; half-life T4= 1 week
parathyroid glands-
not slide
4 small OVOID MASSES, 3x6mm each in total 0.4g, 2 parts sup+inf
location: behind thyroid gland embedded in its capsule
blood: highly vasc from inf thyroid a
TRABECULAE epithelium
thin capsule extends to septa. stroma has SPARE RETICULAR CT supporting the dense cluster of secretory cells
embryo:
embryonic PHARYNGEAL POUCH separates sup gland from 4 pouch and inf gland from 3 pouch (same as thymus)
ascending of parathyroid gland misdirected during development so # and location differ
- 10% people parathyroid attaches to thymus
2 cells: chief+oxyphil
CHIEF cells: SMALL polygonal cells w round nuclei +PALE staining. ACIDOPHILIC cyto w IRREG shaped granules- store polypeptide parathyroid hormone PTH (reg Ca in blood)
-targets: 1) osteoblast, responds by producing osteoclasts stimulating factor (increase reabsorption of bone matrix, release Ca suppress PTH. 2) PTH increases reabsorption of Ca in distal convoluted tubules but inhibit reabsorption of PHOSPHATE at proximal convulated tubule. 3) PTH stimulates vit d indirectly stimulate ca reabsorption in small intestine
OXYPHIL cells considered derivative of PRINCIPAL cells: small population (LESS ABUNDANT), CLUSTERED. common in OLDER patients. LARGER, than chief, very ACIDOPHILIC cyto DARKER nuclei, abnormal shaped mito. (usually have low PTH suggests its a derivative of chief cells)
pineal gland
diseases (2)-
not slide
location: in *EPIPHYSIS CEREBRI
F: reg DAILY RHYTHYMS of bodily functions
origin: NEUROENDODERM in post wall of third ventricle + attached to brain by stalk
small, pine shaped, 5-8mm by 3-5mm
- covered by *CT of PIA MATER extends to form septa w small vessels, divide glands into lobules
PINEALOCYTES
ABUNDANT SECRETORY CELLS w vesicles w high MITO. slightly BASOPHILIC cyto w IRREG EUCHROMATIC NUCLEI. has long CYTO PROCESSES that extend to vasc septa and ends in dilation near capillaries (to release in capillary). UNMYELINATED sympathetic n fibers that enter pineal gland end in pineocytes w forming SYNAPSE
- produce MELATONIN: low molecular weight TRYPTOPHAN derivative. melatonin INCREASE DARK, decrease in light. Melatonin causes RHYTHMIC CHANGES of pituitary, hypothalamus according to circadium rhythm and light/dark
cycle of light+darkeness detected by RETINA -> HYPOTHALAMIC TRACT-> SUPRACHIASMATIC nuclei-> unmyelinated sympathetic n fibers-> synapse pineal gland act as NEUROENDOCRINE TRANSDUCER (sensory input to hormonal function)
modified ASTROCYTE =interstitia glial cells
- 5%, found between perivasc area + between groups of pinealocytes. ELONGATED NUCLEI more HEAVILY STAINED (GFAB- glial fibrillar acidic protein) stained than pineocytes.
CORPORA ARENA=brain sand
Ca+Mg formed by mineralization of EC protein deposits
increases w AGE w no affect on gland
HYPERPARATHYROIDISM- decrease P and increase Ca cause deposit of Ca in kidneys +arteries
causes OSTEITIS FIBROSA CYSTICA: bone disease increases OSTEOCLAST and multiple bone cavity
HYPOPARATHYROIDISM- increases P, decreases Ca. bones denser + more mineralise
