The Adrenal Glands Flashcards
Where are the adrenal glands?
Above the kidneys
Right at the back of the abdomen and protected by the ribs
What is the blood supply to and from the adrenal glands like?
Supplied by many (57) arteries that branch of the abdominal aorta
But drain into only 1 vein. The inferior vena cava
How does each gland drain specifically?
The right drains directly into the inferior vena cava
The left drains into the renal vein then the ivc
(Be able to draw this)
What is the anatomy of the adrenal glands?
Outer cortex and an inner medulla
The cortex is comprised of three layers: zona glomerulosa. Zona fasciculata. Zona reticulatis
What does the cortex secrete?
Corticosteroids and sex hormones
Eg. Cortisol
What does the medulla secrete?
Catecholamines
Eg. Adrenaline and noradrenaline
What are catecholamines?
Secreted by adrenal medulla
Synthesised from amino acids
Eg. Adrenaline
What are corticosteroids?
Secreted by adrenal cortex
Synthesised from cholesterol
Includes: mineralcorticoids (aldosterone). Glucocorticoids (cortisol) and sex steroids (oestrogens and androgens)
Which part of the adrenal cortex makes what?
Zona glomerulosa: aldosterone (mineralocorticoid)
Zona fasciculata and zona reticularis: cortisol (glucocorticoid) and tiny amounts of androgens and oestrogens
What is an enzyme?
Protein that catalysed a specific reaction
How are mineralocorticoids formed (aldosterone) ?
Cholesterol —> pregnenolone (side chain cleavage enzyme)
Pregnenolone —> progesterone (3 beta hydroxy steroid dehydrogenase/ 3 beta HSD)
Progesterone —> 11 deoxy corticosterone (21 hydroxylase)
11 deoxy corticosterone —> corticosterone ( 11 hydroxylase)
Corticosterone —> aldosterone (18 hydroxylase)
For aldosterone it’s 21,11,18
How are glucocorticoids formed (cortisol)?
Cholesterol —> pregnenolone (side chain cleavage)
Pregnenolone—> progesterone (3 beta HSD)
Progesterone —> 17 hydroxy progesterone (17 hydroxylase)
17 hydroxy progesterone —> 11 deoxy cortisol (21 hydroxylase)
11 deoxy cortisol —> cortisol (11 hydroxylase)
Cortisol goes 17,21,11
What does aldosterone do?
Main effect is for sodium reabsorbtion in the kidney
Stimulates Na+ reabsorbtion in distal convoluted tubule and collecting duct
Also stimulates K+ and H+ secretion
It switches on the Na+/K+ ATPase
This increases water reabsorbtion and blood volume
How is aldosterone regulated?
Renin
Decreased renal perfusion pressure (associated with decreased arterial blood pressure)
Increased renal sympathetic activity (direct to juxtaglomerular apparatus cells) (these feel the change is pressure)
Decreased Na+ load to top of loop of henle
So a high BP surprises renin
Renin—>aldosterone—> raises BP
How does renin affect aldosterone secretion?
The liver releases angiotensin
Renin converts angiotensin to angiotensin I
ACE converts angiotensin 1 to angiotensin II
Angiotensin II regulates aldosterone secretion
It activates the enzymes: side chain cleavage, 3 beta HSD, 21 hydroxylase, 11. Hydroxylase, 18 hydroxylase
What does cortisol do?
Normal stress response (fight or flight)
Metabolic effects: peripheral protein catabolism, gluconeogenesis, increases blood glucose levels, lipolysis in adipose, enhanced effect of glucagon and catecholamines
Weak mineralocorticoid effects
Renal and cardiovascular effects: excretion of water load, increased vascular permeability
How is cortisol secretion regulated?
ACTH (adrenocorticotropic hormone)
What does the hypthalamo pituitary adrenal axis look like?
Hypothalamus: CRH (corticotropin releasing hormone)
Pituitary: ACTH (adrenocorticotropic hormone)
Adrenal glands: cortisol
Cortisol has a negative feedback effect on both the hypothalamus and pituitary (should be able to draw this)
What is the effect of ACTH on the adrenal glands?
Activated enzymes:
side chain cleavage
3 beta HSD
21 hydroxylase
11 hydroxylase
17 hydroxylase
Cortisol has a diurnal rhythm, what does this mean?
Follows the circadian cycle
Lowest at midnight
Peaks around 9am
What is Addison’s disease?
Primary adrenal failure
Autoimmune disease where the immune system destroys the adrenal cortex, or more commonly caused by tuberculosis
Doesn’t produce enough cortisol or aldosterone
Pituitary secretes lord of ACTH due to lack of negative feedback (And MSH (melanocyte stimulating hormone) this helps with tanning
What are some symptoms of addisons?
Low blood pressure
Vitiligo
Tanning
Weight loss
Nausea
Diarrhoea
Vomiting
Crisis: syncope, fever, convulsions, hypoglycaemia, hyponatraemia, vomiting
How is addisons treated?
Hydrocortisone or another glucocorticoid (such as pregmisolone)
To treat a crisis, rehydrate with saline, give dextrose to prevent hypoglycaemia
What is Cushing’s syndrome?
An excess of cortisol
May be due to an adrenal tumour or a pituitary tumour, taking steroids by mouth, ectopic ACTH (lung cancer)
What are some symptoms of cushings?
Depression
Fat pads
Easy bruising
Red stretch marks
Poor wound healing
Weak muscles
Diabetes
Lemon on sticks
Thin skin
Proximal myopathy
Moon face
How are catecholamines made (adrenaline and noradrenaline)?
FroM tyrosine
Then tyrosine
Then noradrenaline
Then adrenaline (same as before but it has a methyl group)
What do catecholamines do?
Fight or flight response (tachycardia, sweating, increased blood glucose)
They are stored in cytoplasmic granules and released in response to acetylcholine from preganglionic sympathetic neurones
They circulate bound to albumin
Degraded by monoamine oxidises and catechol-O-methyl transferase
