The adrenal gland Flashcards
Where are the adrenal glands
Above the kidneys
veins and arteries of adrenal glands
Left adrenal vein drains into renal vein
Right adrenal vein drains into IVC (inferior vena cava)
Both adrenals have many arteries but only one vein
MICroanatomy of adrenal glands and where exactly is adrenaline made and cortisol
Adrenal medulla secretes catecholamines (adrenaline)
Adrenal cortex secretes corticosteroids (cortisol)
Adrenal cortex made up of zona reticularis, zona fasciculata, zona glomerulosa
What are catecholamines
Adrenaline / epinephrine (80%)
Noradrenaline / norepinephrine (20%) (dopamine)
What are corticosteroids
Mineralocorticoids (aldesterone)
Glucocorticoids (cortisol)
SEx steroids (androgens, oestrogens)
Where is aldosterone and cortisol found
Aldosterone : zona glomerulosa
Cortisol - Zona fasciculata and zona reticularis
1000 times more cortisole than aldesterone
Section of tissue of the adrenal cortex : microanatomy
The adrenal cortex microanatomy diagram
Blood carries the aldosterone thru vesiculata as it picks up cortisol etc and then will all come out of this vein
What is a steroid
- Comes from cholesterol
- ADrenal gland secretion precursor is cholesterol
- Not all are same - may have diff effects
- cholesterol has 27 C atoms
- Oxidation of different carbons drives the production of the adrenal hormones
How is aldesterone and cortisol produced by enzyme action on cholesterol
ENzymes are hydroxylases
Eg 17 hydroxylase
specific enz catalyse the synthesis of alterations to the molecule
Why may some people not produce enough cortisol
Missing enz such as 21 hydroxylase
Aldesterone mechanism of action
Kidney takes blood and produces urine
Glomerulus filters urine
Tubules swaps out things you don’t need and things you need
Controlled by aldosterone
Switches on enzymes sodium and potassium atpases
Reabsorb Na+ and water in distal convoluted tubule and corticol collecting duct, and lose K+ and H+ maintaining blood pressure in same areas
Xs K - Potassium is lost in urine
So controls bp, sodium and lowers K
renin relase when blood pressure falls
When blood presure falls - produce renin
Goes into circulation
Switches on cascade
Liver makes basic protein
If there is decreased renal perfusion pressure (decreased arterial BP)
=> Increased renal sympathetiv actvity
(direct to JGA cells)
=> Decreased Na+ load to top of loop of Henle
Renin stimulates activation
Effects of angiotensin II on adrenals
Angiotensin II stimulates aldosterone production in the zona glomerulosa in the adrenal medulla
Side chain cleavage
activates enzymes for production of aldosterone (3-hyroxysteroid dehydrogenase; 21, 11, 18 hydroxylases)
Cholesterol initiates chain reaction switching on enz - happens when you see more angiotensin II
Physiological effects of cortisol
Normal stress response
Metabolic effects
- peripheral protein catabolism
- hepatic gluconeogenesis
- increased blood glucose concentration
- fat metabolism (lipolysis in adipose tissue)
- enhanced effects of glucagon and catecholamines
Weak mineralocorticoid effects
Renal and cardiovascular effects
- excretion of water load
- increased vascular permeability
When there is too much cortisol, negative feedback suppression of CRH and ACTH
Cortisol changes way you use energy - makes you break down protein - converted to glucose to keep you alive - blood gluc increase, breaks up fat locally
Adenohypophysis feedback
Effects of ACTH on adrenals
ACtivates same enz as angiotensin execept 18 hydro - replaced with 17 hydroxylase
Cortisol has …. rhythm
diurnal circadian rhythm
It is low at midnight
Addisons disease
- Primary adrenal failure
- Autoimmune disease where the immune system destroys the adrenal cortex
- Tuberculosis of the adrenal gland
- Pituitary starts secreting loads of ACTH and thus MSH
- Increased pigmintation
- Autoimmune vitilligo
- No cortisol or aldosterone so low BP
- Cortisol deficiency
- Aldosterone deficiency
- Salt loss
- Low blood pressure
- Eventual death
Why do patients with addisons have a good tan
The pigmentation is caused by increased levels of MSH which comes hand in hand with increased ACTH
Both ACTH and MSH and endorphins come from the large precursor protein Pro-opio-melanocortin (POMC) which is broken down to form many smaller hormones
HIgh level of ACTH - increased MSH - stimulates skin cells to freckle and then tan
Summary of addisons
cortisol deficiency
Aldosterone deficiency
salt loss
Low bp
Eventual death
Treatment of Addisonian crisis
Rehydrate with normal saline
Give dextrose to prevent hypoglycaemia which could be due to the glucocorticoid deficiency
Give hydrocortisone or another glucocorticoid
What is cushings syndrome
too much cortisol (or other glucocorticoid) caused by a tumour of the adrenal gland of tumour of pituitary (excess ACTH)
Symptoms of cushings
Thin skin
Proximal myopathy
Centripetal obesity (lemon on sticks) (thin legs and arms but obesity)
Diabetes, hypertension and osteoporosis
Immunosuppression (reactivation of TB)
Moon face
Red Striae (stretch marks - body cant make protein fast enough for fat deposition)
Easy bruising
Depression
POor wound healing
Fat pads (because tumour makes ACTH continuosly - adrenal gland gets bigger - cortisol gets around body - fat pads develop)
What causes cushings
- Xs of cortisol or other glucocorticoid
- Taking steroids
- Pituitary adenoma
- Ectopic ACTH (lung cancer) (can express random genes and so too much cortisol may be produced)
- Adrenal tumour
what are catecholamines
Adrenal hormones
Medulla is derives from the ectodermal neural crest
Tyrosine is the precursor for Adr and NA synthesis
Catecholamines are stored in cytoplasmic granules & are released in response to Ach fom preganglionic sympathetic neurones
Dop secreted rapidly
role of catecholamines
‘Fight or flight response’ e.g. tachycardia, sweating, increased blood glucose, alertness, vasoconstriction
NA & Adr circulate bound to albumin
Degraded by two hepatic enzymes: monoamine oxidase & catechol-O-methyl transferase
The adrenal gland
Microanatomy pic
Hpa axis pic
