8 - The adrenals and their hormones Flashcards
Where are the adrenals glands?
on the superior poles of each of the 2 kidneys
Describe the blood supply and drainage of the adrenal glands?
have many arteries BUT ONLY ONE VEIN
Where do the right and left adrenal veins drain into?
right - into IVC
left - into renal vein —> IVC
What are the layers of the adrenal gland?
cortex (outer part) consists of 3 zones - zona glomerulosa - zona fasciculata - zona reticularis adrenal medulla (centre)
What is produced in the different layers of the adrenal glands?
cortex - produces corticosteroids - zona glomerulosa - aldostérone - zona fasciculata - cortisol - zona reticularis - sex hormones adrenal medulla - catecholamines
What is the pattern of cells in the different zones of the cortex?
zona fasciculata - cells line up as strings
zona reticularis - doesn’t have a pattern
What are the 2 ways that blood passes through the cells?
- most of it passes through the cells (diffusion)
- there are some vessels which go through the cortex to get to the medulla
What is the medulla of the adrenals made up of?
chromaffin cells (specialised post-ganglionic nerve fibres in a specialised form)
this means there is a part of the sympathetic NS where the cells innervated by the pre-ganglionic fibres will release their hormones (as hormones) into the general circulation
What hormones are produced by the adrenal medulla?
CATECHOLAMINES:
- adrenaline (80%)
- noradrenaline (20%)
- dopamine (very low concs)
What types of hormones are produced by the cortex? Give examples
CORTICOSTEROIDS - mineralocorticoids e.g. aldosterone GLUCOCORTICOIDS - cortisol SEX STEROIDS - androgen - oestrogens
What hormones are produced from the gonads?
progestogens
androgens
oestrogens
In the synthesis of adrenal cortisol hormones, what is the first conversion step?
cholesterol —–> pregnelonone
What is progesterone a precursor of?
aldosterone
What is the precursor of oestrogens?
androgens
Compare the percentage of corticosteroids that are bounds to plasma proteins
a lot more aldosterone is unbound in the blood compared to cortisol
cortisol is a lot more more selective for CBG (corticosteroid binding globulin)
CORTISOL: 75% - bound to CBG 15% - albumin 10% - unbound ALDOSTERONE: 60% - bound to CBG 40% - free/unbound
What are the receptors for the different corticosteroids?
cortisol —-> glucocorticoid receptor
aldosterone —–> mineralocorticoid
HOWEVER, cortisol can also bind to mineralocorticoid receptors
If cortisol binds to both kinds of receptors, why is aldosterone needed?
there are tissues within the body that exclude cortisol - aldosterone is required here
NOTE: the enzyme 11hsd2 metabolises cortisol and is present in these tissues (kidney and tissue_, therefore, aldosterone had major impacts here
What part of the kidney nephron does aldosterone act on?
DCT and cortisol collecting duct
What effect does aldosterone have on osmolality?
What effect does this have?
increases osmolality
this simulates the release of vasopressin, which works on the collecting duct to increase water reabsorption
(overall, the effect of aldosterone is an expansion of extracellular fluid volume)
What condition usually has aldosterone as its most important clinical correlate?
hypertension
What stimulus do macula dense respond to?
changes in the sodium ion concentration
What do the juxta-glomerula cells produce?
Renin - an enzyme (important in the production of aldosterone)
What does angiotensin II do?
- stimulates the zona glomerulosa to produce aldosterone
- a vasoconstrictor
What is the main stimulus for cortisol?
stresssssssssss
