Adrenals Flashcards
Adrenals are one of the most highly perfused organs in the body;
2000 cc/kg/min
Where do adrenal cortex and medulla arise from?
cortex–> mesoderm
medulla–> ectoderm; neural crest origin
What is the blood supply of the adrenal glands?
superior adrenal arteries–> from inferior phrenic arteries
middle adrenal arteries–> from aorta
inferior adrenal arteries–> from renal arteries
What is special about the venous drainage of the adrenal glands?
left adrenal vein is longer; drains into inferior phrenic veins–> which drains in left renal vein–> IVC
right adrenal vein is shorter; drains directly into IVC
Where does right adrenal vein drain into?
directly into IVC
Left adrenal vein drains where?
its longer
drains into left inferior phrenic vein; then left renal vein; then into IVC
what are the three layers of the adrenal cortex?
outer zona glomerulosa;
middle zona fasciculata;
inner zona reticularis
Outward to inward, what are the layers of the adrenal cortex?
glomerulosa
fasciculata
reticularis
In what part of adrenal medulla do we see an interface between sympathetic NS and endocrine system?
adrenal medulla
sympathetic fibers synapse with chromaffin cells
What converts norepinephrine into epinephrine?
phenylethanolamine n-methyl tranferase
PNMT
Zona glomerulosa makes what hormone?
aldosterone
Highest levels of ACTH and thus cortisol are seen when?
early morning when we wake
What do glucocorticoids do?
have a net catabolic effect
Aldosterone released from what zone?
zona glomerulosa
How does aldosterone get released from zona glomerulosa?
RAAS
low Na is detected in distal convoluted kidney tubule (seen in septic shock, hypovolemia)
renin is released from JGA
renin then cleaves angiotensinogen (made in liver) to angiotensin I
Angiotensin I cleaved to AT II by ACE in lungs
ATII is a potent vasoconstrictor–> stimulates aldosterone release
How does K affect aldosterone release or the RAAS?
hypo-kalemia reduces aldosterone released by suppressing renin release
hyper-kalemia; opposite effect
What does aldosterone do?
regulates circulating fluid volume and electrolyte balance
promotes Na/Cl retention in distal convoluted tubule
K/H are secreted into urine
negative feedback occurs when too much Na is seen at distal convoluted tubule, suppressing renin release
Where are catecholamines synthesized in the adrenals?
medulla
Adrenal medulla makes what?
catecholamines
Synthesis of catecholamines in adrenal medulla begins with what?
tyrosine
How is epinephrine made?
tyrosine–> L-dopa–> Dopamine–> Norepi–>Epi
Norepi is converted to epinephrine by actions of phenylethanolamine n-methyl transferase, which is located where?
chromaffin cells of adrenal medulla
and in the organ of Zuckerkandl
How are catecholamines released from adrenal medulla?
sympathetic stimulation of adrenal medulla causes release of stored catecholamines
What is the net effect of adrenal medulla catecholamine release?
deliver blood and oxygen to brain, heart and muscle at the expense of the rest of the body
fight-or-flight response