Adrenal anatomy and physiology Flashcards
Describe the appearance and location of the adrenal glands
small Y shaped glands located extraperitoneally at the upper poles of the kidneys
They have an outer cortex - 90%
They have an inner medulla - 10%
Where does the arterial blood supply to the adrenal glands arise from
The renal arteries, aorta and inferior phrenic artery
Where is the venous drainage from the adrenal glands
central vein into the inferior vena cava on the right and the let renal vein on the left
What is the adrenal cortex derived from
mesodermal tissue
what is adrenal medulla derived from
neuroectodermal tissue (embryonic neural crest
What are the 3 zones of the cortex
zona glomerulosa - secretes mineralocorticoids (aldosterone)
Zona fasciculata - secretes glucocorticoids (cortisol)
Zona reticularis - secretes androgenes
What is the adrenal medulla composed of
chromaffin cells
What do chromaffin cells produce
catecholamines (adrenaline, noradrenaline, dopamine) from the amino acid tyrosine
What stimulates catechumen secretion
preganglionic sympathetic nerves
What stimulates aldosterone stimulation
Renin-angiotensin system and elevated serum potassium
Where is renin synthesised and stored
in the juxtaglomerular apparatus in the kidney
How does renin work
It cleaves angiotensinogen to angiotensin 1
this is then converted to angiotensin 2 by angiotensin-converting enzyme on the luminal surface of capillaries in the lungs
What does angiotensin 2 cause
stimulation of aldosterone secretion resulting in sodium retention and potassium loss in the kidney
What stimulates renin release
reduced renal perfusion pressure and blood flow, reduced sodium concentration in the renal tubules and increased renal sympathetic activity
What is aldosterone
a lipid-soluble hormone that crosses plasma membranes and binds to intracellular receptors.
What does Aldosterone increase
sodium and water reabsorption and potassium secretion in the kidney
What stimulates cortisol release
Adrenocorticotrophic hormone (ACTH)
ACTH is released from where and stimulated by what
Anterior pituitary
stimulated by hypothalamic corticotrophin releasing hormone (CRH)
What does cortisol inhibit
ACTH and CRH production
How does cortisol increase hepatic gluconeogenesis
enhancing the expression of enzymes involved in gluconeogenesis such as glucose-6-phosphatase and phosphoenolypyrivate carboxykinase (rate limiting enzyme in gluconeogenesis)
Increasing the availability of substrates, for example glycogenic amino acid and glycerol by stimulating proteolysis (in skeletal muscle) and lipolysis respectively
What do glucocorticoids do to glucose
They inhibit glucose uptake
What does cortisol have an effect on in terms of the immune system
T cell and B cell mediated immune responses as well as suppressive effects on monocytes and neutrophils
Adrenal androgens synthesis are under the control of what
ACTH
What are the 2 main catecholamines produces by the adrenal medulla
Adrenaline (80%)
Noradrenaline (20%)
