adrenal gland Flashcards
where are the adrenal glands located
above the kidneys
where does the left adrenal vein drain into
the renal vein
where does the right adrenal vein drain into
the inferior vena cava (IVC)
how many veins and arteries do the adrenals have
many arteries but only 1 vein
microanatomy of the adrenal glands
adrenal cortex which has 3 layers - zona glomerulosa/fasciculata/reticularis
adrenal medulla
what does the adrenal cortex secrete
corticosteroids
what does the adrenal medulla secrete
catecholamines
what does the adrenal medulla do
secretes catecholamines by neuroendocrine/chromaffin cells
adrenaline/epinephrine 80%
noradrenaline/norepinephrine 20%
dopamine
what does the adrenal cortex do
secretes corticosteroids
mineralocorticoids (aldosterone)
glucocorticoids (cortisol)
sex steroids (androgens, oestrogens)
what zona secretes aldosterone
zona glomerulosa
what zona secretes cortisol (androgens and oestrogens)
zona fasciculata and reticularis
where do steroid hormones come from
cholesterol
what is the precursor for adrenal gland secretions
cholesterol
how many carbons does cholesterol have
27
what is an enzyme
a protein that catalyses a specific reaction
various enzymes are present in cells
specific enzymes catalyse the synthesis of particular alterations to the molecule
what is the pathway to get from cholesterol to aldosterone
cholesterol undergoes side chain cleavage > pregnenolone
pregnenolone is oxidised by 3 beta hydroxysteroid dehydrogenase > progesterone
progesterone is oxidised 3 times by 21, 11, 18 hydroxylases > aldosterone
what is the pathway to get from cholesterol to cortisol
cholesterol undergoes side chain cleavage > pregnenolone
pregnenolone is oxidation by 3 beta hydroxysteroid dehydrogenase > progesterone
progesterone is oxidised by 17, 21, 11 hydroxylases to form cortisol
what does aldosterone do
controls blood pressure
conserves Na by stimulating its reabsorption
stimulates K+ and H+ secretion
where does aldosterone stimulate Na reabsorption and K+/H+ secretion
in distal convoluted tubule and cortical collecting duct in the kidney
and in sweat glands, gastric glands and colon - Na reabsorption
how is aldosterone regulated (4)
- by renin release when blood pressure falls (stimulates other cells)
- increased renal sympathetic activity (directed to JGA cells) juxtaglomerular apparatus
- decreased Na+ load to the top of loop of Henle (macula densa cells)
- noradrenaline
what is associated with decreased arterial blood pressure
decreased renal perfusion pressure
what does renin do
stimulates conversion of angiotensinogen to angiotensin 1
what converts angiotensin 1 to 2
ACE
what does angiotensin 2 do
regulator of aldosterone release binds to receptors in zona glomerulosa causes vasoconstriction (increased BP)
what does aldosterone do
increases blood volume > increases BP
what are the effects of angiotensin 2 on the adrenals
activation of the following enzymes side chain cleavage 3 hydoxysteroid dehydrogenase 21 hydroxylase 11 hydroxylase 18 hydroxylase
summary of action of aldosterone
cholesterol > aldosterone > controls BP, increases sodium and lowers potassium
when is cortisol released
normal stress response
what are metabolic effects of cortisol
peripheral protein catabolism (break down for energy)
hepatic gluconeogenesis
increased blood glucose concentration
fat metabolism (lipolysis in adipose tissue)
enhanced effects of glucagon and catecholamines
other effects of cortisol
weak mineralocorticoid effects
renal and cardiovascular effects - excretion of water load, increased vascular permeability
how is cortisol secretion regulated - ACTH
negative feedback at 2 levels
effects of ACTH on the adrenal glands
activation of these enzymes side chain cleavage 3 beta hydroxysteroid dehydrogenase 17 hydroxylases 21 hydroxylases 11 hydroxylases
what rhythm does cortisol have
diurnal and circadian
what is addisons disease
primary adrenal failure
an autoimmune disease where the immune system decides to destroy the adrenal cortex
tuberculosis of the adrenal glands
the pituitary starts secreting lots of ACTH and hence MSH (melanocyte stimulating hormone?) > increased pigmentation > autoimmune vitiligo may coexist
no cortisol or aldosterone > low blood pressure
cortisol and aldosterone deficiency
salt loss
low BP eventual death
symptoms and signs of addisons
hyperpigmentation low bp weakness weight loss gastrointestinal (nausea, diarrhoea, vomiting, constipation, abdominal pain) vitiligo
what does an addisonian/adrenal crisis consist of
fever syncope (fainting) convulsions hypoglycaemia hyponatremia - low sodium severe vomiting and diarrhoea
what is POMC
pre-opio melanocortin
a large precurosor protein that is cleaved to form a number of smaller peptides - ACTH, MSH and endorphins
so people with pathologically high ACTH may become tanned
urgent treatment of addisonian crisis
rehydrate with normal saline
give dextrose (glucose) to prevent hypoglycaemia which could be due to glucocorticoid deficiency
give hydrocortisone or another glucocorticoid
what is Cushings syndrome
too much cortisol due to adrenal tumour or tumour of pituitary (more ACTH)
cortisol inhibits protein synthesis
excess cortisol or other glucocorticoid
causes of Cushings syndrome
taking steroids by mouth (common) - asthmatics
pituitary dependent cushings disease (pituitary adenoma)
ectopic ACTH (lung cancer) - wrong place
adrenal adenoma or carcinoma (tumour)
symptoms and signs of Cushings
moon face red cheeks fat pads - buffalo hump mental changes eg depression thin skin easy bruising impaired glucose tolerance (diabetes) high blood pressure proximal myopathy (muscle weakness) thin arms and legs red striae pendulous abdomen poor wound healing
what is the role of catecholamines
fight or flight response
tachycardia, sweating, increased blood glucose, alertness, vasoconstriction
how does NA and A circulate in the blood and what is it degraded by
bound to albumin
degraded by 2 hepatic enzymes - monoamine oxidase and catechol-O-methyl transferase
where is the adrenal medulla derived from
ectodermal neural crest
what is the precursor for NA and Adr synthesis
tyrosine
where are catecholamines stored
in cytoplasmic granules and released in response to ACh from preganglionic sympathetic neurones
how is dopamine made
tyrosine is oxidised to dopa
dopa is oxidised to dopamine
how is dopamine made
tyrosine is oxidised to dopa
dopa is oxidised to dopamine
where does adrenaline come from
dopamine
by oxidation and then methyl addition to become epinephrine
