Endocrine I and II Flashcards
hypothalamus
neurosecretory cell pathway
produce nuerosecretory hormones >
anterior glandular lobe of pituitary gland via primary and secondary fenestrated capillary plexus + hypophyseal portal veins
neurosecretory products
SRH/GHRH
TRH
CRH
GnRH
anterior lobe contains
chromophils (acid/basophils) + chromophobes
acidophils
somatotrophs + lactotrophs (mammotrophs)
somatotrophs
stimulated by SRH/GHRH
inhibited by somatostatin
release somatotropin (growth hormone)
excessive GH in KIDS=gigantism from somatotrophic adenoma/tumor
in ADULTS=acromegaly (enlarged face, jaw, tongue, hands, feet, organs)
lactotrophs
aka mammotrophs
stimulated by PRH and TRH
inhibited by dopamine
release prolactin (for mammary glands when pregnant)
prolactinoma most common benign pituitary tumor
basophils
corticotrophs + thyrotrophs + gonadotrophs
corticotrophs
stimulated by CRH
release ACTH precursor > adrenal cortex > cortisol and corticosterone
thyrotrophs
stimulated by T-RH
release TSH (thyrotropin) >thyroid>T3T4
gonadotrophs
stimulated by GnRH
release FSH and LH > ovary and testis
hypothalamohypophyseal tract
supraoptic and paraventricular nuclei of hypothalamus
have cell bodies of neurosecretory neurons > axons make up tract > terminates in posterior lobe/neural of pituitary gland
axons and terminals have vasopressin (ADH) and oxytocin
posterior lobe contains
- herring bodies (granules of ADH or oxytocin)
- pituicytes (glia-like support cells)
- fenestrated capillaries
ADH = yellow urine, oxytocin = contractions in childbirth
thyroid gland produces
- T3 (triiodothyronine) - follicular cells
-
T4 (tetraiodothyronine)- follicular cells
-both reg cell/tissue metabolism and heat production -
calcitonin- parafollicular cells
-reg blood calcium levels
T3 and T4 production
T4 only from follicular cells in 20:1 ratio, T3 x5 more potent than T4
T3 converted from T4 by heart, liver, kidneys
thyroid hormone synthesis
- follicular cells syn thyroglobulin (glycoprotein) w/ 120 tyrosine residues
- release into follicular lumen
- iodide (inactive) from bloodstream pumped into follicular cells
- iodide oxidized on apical membrane/colloid facing side into iodine (active) and stays there
- iodine iodinates tyrosine residues = MIT + DIT
- MIT + DIT = triodinated thyronine
- DIT + DIT = tetraiodinated thyronine
- follicular cells uptake colloid from lumen
- proteases cleave iodinated tyrosine residues from thyroglobulin into cell cytoplasm = uncoupled MIT + uncoupled DIT + T3 + T4
- thyroid hormones (inactive) released from basal aspect into extracellular space
- fenestrated capillary network
- general circulation
- activated in target tissues and organs
lysosomal pathway, main
exocrine glands vs endocrine glands
exocrine = products released into ducts
endocrine = products/hormones released into extracellular space > bloodstream > organs
hypothalamus
nucleus in the brain
coordinates endocrine functions and integrates endocrine/ANS functions
has neurons = neurotransmitters AND
neurosecretory cells = hormones
neurosecretory hormone pathway
general
- syn in hypothalamus
- transported to axon terminals
- released into ECS
- pass into primary capillary plexus
- flow into hypophyseal portal veins
- secondary capillary plexus (sinusoidal) @anterior pituitary
- parenchyma of anterior pit to influence basophils/eosinophils
thyroid gland
general structure
R lobe + isthmus (bridge) + L lobe + pyramidal lobe
surrounded by capsule of dense irreg/coll CT from deep cervical fascia
trabeculae/septa- partion into lobules and carry vessels and nerves into gland
parathyroid glands
4 @ thyroid capsule on posterior surface of thyroid gland
thyroid follicles
follicle is basic structural/functional unit of thyroid gland
spherical cyst like + lumen w/ colloid and thyroglobulin
thyroid follicle histology
simple squamous = low level activity
simple cuboidal = normal activity
simple columnar = highly active
surrounded by basal lamina + reticular fibers + fenestrated capillary plexus
parafollicular cells
from neural crest
b/t follicles so not exposed to colloid @ basal lamina near capillaries
syn calcitonin and store it in granules
calcitonin
released when blood calcium levels elevated
lowers blood Ca levels to normal via inhibiting osteoclasts AND promote Ca deposition in bones
thyroglobulin synthesis
follicular cells syn in RER when activated by TSH
glycosylation in RER and Golgi
released into lumen via exocytosis
iodine pathway
thyroid hormone synthesis
- iodine from diet > reduced to iodide in GI
- bloodstream
- pumped into follicular cells via sodium/iodide symporters
- diffuses to apical cell membrane
- iodide ions pumped into lumen via iodide/chloride transporter (pendrin)
- thyroid peroxidase oxidizes iodide into iodine
- thyroid peroxidase catalyzes iodination of thyroglobulin
thyroglobulin processing pathways
TSH binds @basal > filopodia form @luminal surface = endocytosis
- lysosomal pathway
- transepithelial pathway
transepithelial pathway
- thyroglobulin binds megalin (TMP on apical membrane facing colloid)
- evades lysosomes and transported to basolateral membrane
- released into blood as T3T4 still bound to thyroglobulin
physiological effects T3T4
inc: cell metabolism, growth rate, mental activity, fatty acid syn
stimulate: endocrine gland function, carb metabolism
dec: formation of phospholipids, triglycerides, cholesterol
increase thyroid hormone
dec body weight
inc heart rate, metabolism, respiration, muscle function, appetite
high levels = tremors, fatigue, impotence, menstrual irregularities
hyperthyroidism
aka toxic goiter or graves disease
autoantibodies bind to TSH receptors = inc colloid uptake = xs thyroid hormones in circulation
exophthalmos (bulging eyes from fibrosis of rectus muscles and acc of loose CT behind eyeball) and enlarged thyroid
cell types in parathyroid glands
- principal- syn/store/release PTH
- oxyphil- inactive principal/chief cells, don’t know function
- intermediate- inactive, don’t know function
PTH
regulates calcium and phosphate levels in blood and ECF
-influences bone, kidneys, GI
inc blood calcium levels to normal if low serum
-high serum Ca inhibits PTH
calcitonin is opposite
islets of langerhans cell types
pancreas
in endocrine portion
- alpha = glucagon (inc blood glucose)
- beta = insulin (dec blood glucose) and amylin (inhibit stomach emptying/glucagon release)
- delta = D (somatostatin-reduce smooth muscle contractions of dig tract) or D1 (vasoactive intestinal peptide- induce glycogenolysis, control smooth muscle tonus and contraction of GI)
- epsilon= ghrelin (induce hunger sensation)
- PP = pancreatic polypeptide (inhibit digestive juices)
- also gastrin by 1+ cells (stim HCl by parietal cells in stomach mucosa)
exocrine portion pancreas
acini + duct system
produces digestive enzymes
suprarenal cortex zones
- zonal glomerulosa- outer, mineralcorticoids (aldosterone main + deoxycorticosterone)
-activate by ACTH and angiotensin II - zona fasciculata- middle/largest layer, glucocorticoids (cortisol + corticosterone)
- zona reticularis- inner, weak androgens (DHEA, androstenedione, glucocorticoids)
suprarenal cortex zones
histology
- zonal glomerulosa- cells in cords and clusters
- zona fasciculata- cells in radial columns w/ capillaries running b/t
- zona reticularis- anastomosing cords w/ lipofuscin
suprarenal medulla
from neural crest, sympathetics
has chromaffin cells = epinephrine and norepinephrine (catecholamines)
release Ach
PTH synthesis
- ribosomes on RER syn preproparathyroid hormone
- @RER lumen = proparathyroid hormone + polypeptide
- @Golgi lumen = parathyroid hormone (PTH) + polypeptide
- stored in secretory granules
PTH in bone
1.binds osteoblast receptors (prolonged)
2.osteoblasts release osteoclast stimulating factor = triggers osteoclasts to breakdown and free Ca and P from bone
or if intermittent = anabolic effect so inc bone mass to treat osteoporosis
PTH in kidneys
conserves Ca
promotes activation of vitamin D
PTH in GI
regulates rate of Ca absorption from GI (directly) and activation of vitamin D (indirect in kidney)
vitamin D facilitates Ca absorption in GI more great than PTH effect
thyroidectomy
complete removal of parathyroid glands = drop Ca levels
tetanic contraction of muscles (laryngeal and respiratory) = death
tetany
hypoparathyroidism > hypocalcemia = tetany
neuromuscular irritability, spontaneous twitching, numbness, tingling
urinary tract stones
from hyperparathyroidism > osteoclasts erode bone = hypercalcemia
stones and calcification of lungs, myocardium, stomach, blood vessels
Diabetes Mellitus
hyperglycemic metabolic disorder from
1. beta cells not produce insulin
2. defective insulin receptors on targets
Type I Diabetes
insulin-dependent
juvenile onset
autoantibodies cause islets to atrophy and fibrotic, not enough insulin produces
signs: polydipsia (thirst), polyphagia (eating), polyuria (urination)
Type II Diabetes
non insulin-dependent
most common
over 40 yr old
Cushing Syndrome
small tumors of basophils in anterior pituitary gland = excess ACTH
suprarenal cortex overstimulated = excess cortisol
obesity in face, neck, trunk, impotence (males) amenorrhea (females)
