TBL20 - Adrenal Glands Flashcards
What forms the primitive adrenal cortex?
Adjacent to the mesonephros, proliferation of mesenchymal cells in the intermediate mesoderm forms the primitive adrenal cortex
What are chromaffin cells formed from and what do they infiltrate? Where do some of the chromaffin cells migrate into?
1) Ectoderm-derived neural crest cells form chromaffin cells that infiltrate the paravertebral and prevertebral sympathetic ganglia
2) Some of the chromaffin cells migrate into the primitive cortex and transform its central portion into the adrenal medulla
What stains the catecholamines reddish brown? Therefore, how can chromaffin cells be designated?
1) Oxidation of epinephrine and norepinephrine by potassium chromate (i.e., the chromaffin reaction) stains the catecholamines reddish brown
2) Thus, cells that synthesize and store the catecholamines are designated chromaffin cells
What nerve fibers synapse with chromaffin cells of the adrenal medulla? What does synaptic activation of these cells result in?
1) Presynaptic fibers of the least splanchnic nerve synapse with chromaffin cells of the adrenal medulla
2) Synaptic activation results in secretion of norepinephrine and epinephrine into the medullary capillaries
What is the clinical consequence of a pheochromocytoma?
1) Pheochromocytomas are tumors of the adrenal medulla
2) Occurring mostly in adults, pheochromocytoma is a neoplasm that arises from catecholamine-producing cells
3) Ensuing elevated levels of epinephrine and norepinephrine released into the blood lead to sustained or intermittent hypertension
Observe the outer cortex and central medulla of the adult adrenal gland.
Okay
What do arteries supply in the adrenal gland?
Arteries enter the gland and either directly supply the cortical capillaries or traverse the cortex to directly supply the medullary capillaries
Where does the venous system of the adrenal gland reside? What does this allow formation of in the medulla?
1) The venous system resides solely in the medulla
2) Thus, the medulla has a dual arterial supply
How does the dual arterial supply of the adrenal medulla contribute to the “fight or flight” response?
1) Recall that cortical capillaries supply blood first through the cortex and then continue through the medulla to empty into the medullary veins
2) Other branches of arteries that enter the adrenal gland course directly to the medulla without branching out through the cortex and are called medullary capillaries
3) During a fight or flight response, vasoconstriction of cortical capillaries allows blood to flow directly to the medullary capillaries and activates chromaffin cells to produce catecholamines
What zones does the cortex of the adrenal gland consist of?
The cortex, which is essential to life, consists of the thin zona glomerulosa beneath the capsule, the thick zona fasciculata, and the thin zona reticularis adjacent to the medulla
What produces renin and what does it stimulate? What does aldosterone do once it circulates to the kidneys? What changes occur in the blood?
1) JG cell-generated renin stimulates cells of the zona glomerulosa to release aldosterone into the cortical capillaries
2) After circulating to the kidneys, aldosterone elevates Na+ resorption across epithelia of the distal convoluted tubules and collecting ducts
3) The resorbed ions subsequently elevate Na+ concentration in the blood (recall renin secretion occurs in response to decreased Na+ concentration in the glomerular filtrate)
What do cells of the zona fasciculata release? What does this released chemical cause in hepatocytes?
1) Cells of the zona fasciculata release cortisol into the bloodstream
2) After circulating to the liver, cortisol stimulates the hepatocytes to synthesize glucose that is both stored as glycogen and released into the circulation
What do cells of the zona reticularis do and what can these chemicals be converted to?
Cells of the zona reticularis mainly synthesize weak androgens that can be converted to testosterone and estrogen in peripheral tissues
