Histo, Parathyroid, adrenal pancreas Flashcards
How many parathyroid glands are there
four
Where do the parathyroid glands sit on thyroid glan
posterior
What cell types are in parathyroid glands
chief cells and oxyphil cells
Describe chief cells of parathryoid
have basophilic cytoplasm with dense secretion and peptide secreting granules
Describe oxyphil cells
eosinophilic because alot of mitochondria
larger with no secretion granules
Which cells secrete product from parathyroid gland
chief cells
Which cell in parathyroid is the only type present until puberty
chief cells
What is the function of chief cell
secrete PTH
what is PTH
counter-regulatory to calcitonin
what are the effects of hyper and hypo calcemia on PTH secretion
hyper suppress PTH
hypo increase PTH
What does PTH do
increase blood Ca and promotes absorption and increases reabsorption from bones
increases PO4 excretion by kidney
decreases Ca secretion by kidney
promotes Vit D uptake and metabolism
What are the exact effects of PTH on bone reabsorption (Ca)
does not directly affect osteoclasts, binds osteoblasts, sitmulates release of cytokine which affects osteoclast
hyperthyroidism leads to what
increased serum Ca, bones loss and renal calculi
What are the 3 ways to regulate Ca metabolism
change bone turnover, change gut absorption and control urinary Ca secretion
what are the affects of calcitonin on bone reabsoprtion
inhibits Ca reabsorption
What is the effect of Vit D
promote Ca uptake from gut
also negative feedback on itself
promotes Pi absorption
promotes Ca reabsorption from kidneys
What do Ca levels look like in calcitonin deficiency
still have normal Ca levels
4 main effects of PTH
increase bone Ca resorption
increase Ca reabsorption in kidney
inhibits Pi reabsorption
increases conversion of Vit D to 1,25 form
what is the net effect of vit D
bone formation
A deficiency in vit d can lead to what
decreased bone formation
What is the major organ of homeostasis
adrenal, suprarenal gland
What are the differences of the 2 main parts of adrenal gland
cortex and medulla
different in embryonic origin
differ in type and function of secretion
What embryologic structure is the cortex from
mesoderm
What is the function of cortex of adrenal gland
secretes corticosteroids and influences Ach and renin
affects carb, protein metabolisma and electrolyte distribution
What embryologic strucutre is the medulla of adrenal gland from
neroectoderm
what is the function of the medulla of adrenal gland
secrete catecholamines(epi, Noreepi), affect HR, smooth m, carb, lipid metabolism influenced by SANs (preganglionics)
Describe innervation of adrenal gland
preganglionic SAN synapse on medullary cells(bypass other ganglia) and postganglionics on vascular structures
Describe blood supply of adrenal gland and explain general reason why
endocrine organs need blood
superior middle and inferior suprarenal aa
What are the 3 intraglandular vascular routes
subcapsular aa short cortical aa long cortical (medullary) aa
Describe the short cortical aa
arise from suprarenal aa and branch as sinusoids in cortex
sinusoids percolate through outer cortex and converge at inner cortex to empty into sinusoids
expose medullary cells to high steroid levels
describe the long cortical aa
penetrate cortex and go directly to medulla
How many blood supplies does the medulla get
2
from cortical sinusoids (capillaries)
medullary aa (direct)
Describe veins of medulla
veins coalesce in medulla to form central vein
What are the 3 layers of cortex of adrenal gland
zona glomerulosa
zona fasciculata
zona reticularis
What kind of fibers affect adrenal gland medulla
both pre and post ganglionic SAN because affect cells AND blood supply
Describe the zona glomerulus
subscapular, spherical to columnar cells
extensive sER with tubular anastomotic network
numerous mitcohondria with flattened cristae
Describe the zona fasiculata
majority
large cells– large lipid droplets
long radially arranged cords, 1-2 cells thick with interspersed extensive capillaries,
mitochondria with round short tubular cristae
well developed sER, many gap junctions
Describe the zona reticularis
smalles population
little lipid, elongate mitochondria
eosinophilic with more glomerulosa or fasiculata
extensive lipofuscin pigment
What is important about the capillary network in cotex
so steroids can be secreted into blood very quickly
Where is steroid hormones derived from
cholesterol
Where is cholesterol stored to be made into steroids
lipid inclusions as fatty acyl esters
Where are the enzymes for steroid synthesis
in mitochondria and sER
What is meant by regional specialization of hormone synthesis in cortex of adrenal gland
means each area of cortex produces a different type
What is the function of the zona glomerulosa
mineralocorticoids (salt)
Aldosterone!
What is the function of the zone fasciculata
glucocorticoids (sugar)
Cortisol!
What is the role of cortisol
affect carb metabolism, anti-inflammatroy which induce conversion of norepi to epi
What is the role of zona reticularis
androgen precursors (sex) dehydroepiandosterone (DHEA) and androstenedione
What does hypersecretion of DHEA cause
precocious puberty in males
virilization and hirsuitism in females
What is the effect of aldosterone
decreased plasma Na or plasma volume leading to renin secretion by kidney JG cells
What is the effect of renin
angiontensinogen to angiotensin I
What is the feedback from angiotensin II
feedback stimulates aldosterone
What is the net effect of aldosterone
expanded fluid volume
increased in blood pressure
Describe the brain’s role on aldosterone secretion
CRH and AVP in anterior pituitary cause release of ACTH which acts on adrenal gland to increase aldosterone release
What stimulates cortisol release
ACTH from pituitary corticotrophs
What else does ACTH cause
increase in sER and decrease cellular lipid (drawing from lipid pool to produce steroid)
increase cortical blood flow
increased cortisol synthesis and secretion
increase cotrical hypertrophy(not zona glomerulus)
What is the result of hypophysectomy
opposite of ACTH effects
What is the purpose of cortisol
increased blood glucose, aa mobilization and gluconeogenesis
antiinflammatory via inhibition of phospholipase A2, histamine and serotonin release
suppress immune response via T cell suppression(IL2) and lyses eosinophils
maintain vascular responsiveness to catecholamines
inhibit bone formation
increase GFR in keidny
decrease REM sleep
Where does cortisol bind
nuclear R in nucleus to promote gene transcription of the glucocorticoid R
A decrease in cortisol would have what effect on BP
hypotension
What is the effect of cortisol on bone formation
decrease type I collagen
decrease osteoblast activity
decrease gut Ca absorption
Why do people with cushings or extra cortisol have increased change psychosis
since decreases REM sleep
How does cortisol increase GFR
cause vasodilation of afferent arterioles
Where are androgen precursors taken up in body and what are their affects
testes and ovaries, stimulates testosterone and estrogen
Which sex rely more on the androgen sex hormones
females,
males make testosterone in other areas to suffice
What are the neuroendocrine target cells in the adrenal medulla
chromaffin cells
What is the role of chromaffin cells and what do they look like
release secretions into blood
look like ganglion cell and basophilic due to presence in rER
Describe the general path of catecholamine synthesis
tyrosine–> DOPA–> dopamine–>norepi–>epi
The chormaffin cells have nissl bodies which are what
large number ribosomes
What is the predominant catecholamine from adrenal medulla
epinephrine
What are the effects of glucocorticoids on epinephrin containing cells
norepi–> epi
What stimulates release of catecholamines from chromaffin cells
Ach fomr preganglionic SAN
What are the effects of epinephrine
increased glycogenolysis, FA mobilization
increas HR and BP
dilatation of coronary and skel mm vasculature
(constrict skin and GI vasculature)
increased alertness (brain stem reticular activiating system)
increased blood glucose
How does epinephrine increase blood glucose
increased glucagon secretion and decreased insulin secretion
why is it a hypothesis that pancreatic islets derive from neural crest
because intra-islet stem cells express neuronal markers(nestin– IM filament)
how do we boradly differentiate betwen iselt cells with acinar cells
receive much much much more blood flow
Where are islet cells derived from
endoderm, likely pancreatic duct
Describe changes in growth of pancreatic islets through life
cells continue to proliferate during childhood
at maturity little capacity for growth and proliferation, except in pregnancy
What influences growth of islet cells during pregnancy
lactogen and prolactin from placenta induce expansion of islet volume
describe differences of islet size in tail and head
in tail more numerous but smaller
head less numerous and bigger
What are the primary secretions from islet cells
insulin and glucagon
what does glucagon promote
production of glucose from liver glycogen and glucose precursors
what is required for insulin secretion
glucose metabolism
describe synthesis of insulin
insulin mRNA carries message to produce pre-proinsulin
signal cleaved and proinsulin is released into rER to golgi apparatus
disulfide bonds formed
linking peptide C is cleaved to yield mature insulin molecule
how are the granules with insulin translocated
microtubules facilitate movememnt
submembranous actin impedes contact with membrane until stimulated and then depolymerizes
requires Ca for vesicular fusion
What are the 4 primary endocrine cell types
Beta-insulin, amylase
alpha- glucagon
delta- somatostatin
PP- pancreatic polypeptide
What are the minor cell types in islets
delta-1: VIP
EC beta cells: secretin, motilin and substance P
epsilon: ghrelin
What is the role of the signal sequence in insulin production
stop translation of protein until it is bound to rER
What is the role of pancreatic polypeptide
stimulate gastric chief cells
inhibit bile secretion and intestinal motility
inhibit pancreatic enzymes and HCO3 secretion
what is the role of VIP
hyperglycemic and glycogenolytic
affects secretory activity and motility in gut
stimulates pancreatic exocrine secretion
What is the role of secretin
sitmulates HCO3 secretion in pancreatic juice
stimulates pancreatic enzyme secretion
describe the role of motilin
increase gastric and intestinal motility
what is the role of substance P
has NT properties
what is the role of ghrelin
sitmulate apetite
Describe the hypothesized organization of islets based off rodent model
B cells in medulla
alpha, delta and PP in thin cortex
If do not find C peptide in plasma what does this mean
insulin may not be formed, because C peptide is not being cleaved
What allows insulin to crystalize
the zinc that links insulin together
describe intercellular communication in islets
junctional via gap junctions
describe blood supply of islets
islets receive more blood supply and flows central to peripheral
What is the islet-acinar axis
efferent blood from islet enters acinar capillaries, so insulin can stimulate acinar cells
What innervates the islets
SAN norepi inhibits insulin and sitmulates glucagon
PAN inn unclear
In prolonged fasting what becomes major source of E
triacylglycerides
What are the effects of insulin on blood level
decrease blood lgucose, decrease aa, FA, ketoacid and K levels in blood too
What are the effects of glucagon in blood
increase glucose, FA and ketoacid in blood
What are the actions of insulin
increase glucose uptake, increase glycogen formation and protein synthesis, and fat deposition and K uptake
decrease glycogenolysis, gluconeogenesis, lipolysis
How does the liver take up glucose
GLUT 2
how do skeletal muscle and adipose tissue take up glucose
insulin dependent GLUT4
How does epinephrine and cortisol modulate insulin effects
downregulate GLUT4
What glucose transporter is in the brain
insensitive to insulin, GLUT3
