The Adrenal Gland Flashcards
Where does the left adrenal vein drain into?
Renal vien (57 arteries)
Where does the right adrenal vein drain into?
IVC (inferior vena cava)
How many arteries and veins do the adrenals have?
Both adrenal have many arteries many arteries but only one vein
What is the zona glomerulosa?
Outer most thin layer and se of enzymes that make aldosterone
What is the zona fasciulata?
Enzymes which make cortisol
What does the adrenal medulla do?
Make adrenaline (secretes catecholamines)
What does the adrenal cortex make?
- corticosteroids
1. Mineralocorticoids (Aldosterone)
2. Glucocorticoids (Cortisol)
3. Sex steroids (Androgens, oestrogens)
What does the adrenal medulla (neuroedncorine/chromaffin cells)?
- catecholamines
1. Adrenaline/epinephrine (80%)
2. Noradrenaline/norepinephrine (20%)
3. [Dopamine]
What does zona reticularis make?
Cortisol (androgens and eostrogens and works with zona fasciluatris) (not really mostly middle zone)
Where do steroid come from?
Cholesterol (27C atom)
What is the adrenal gland secretion precursor?
Cholesterol
What is an enzyme?
- 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 synthesis of aldosterone?
- Cholesterol
- Side chain cleavage
- Left with pregneolone
- Then enzyme 3 beta hydroxy steroid dehyrogenase (oxidation Zoe)
- Progesterone
- Enzyme: 21 hyroxylase
- 11 deoxycorticosterone
- 11 hydroylase
- Corticosterone
10, 18 hydroxylase - Aldosterone (control blood pressure )
What is synthesis of
- Cholesterol
- Side chain cleavage
- Left with pregneolone
- Then enzyme 3 beta hydroxy steroid dehyrogenase (oxidation Zoe)
- Progesterone
- 17 hydroxylase
- 17 hydroxy progesterone
- 21 hydroxylase
- 11 deoxy cortisol
- 11 hydroxylase
- Cortisol
What does aldosterone do?
- Stimulates Na+ reabsorption in distal convoluted tubule and cortical collecting duct in kidney (and in sweat glands, gastric glands, colon)
- Stimulates K+ and H+ secretion, also in distal convoluted tubule and cortical collecting duct
-Major net effect is to conserve body sodium by stimulating its reabsorption
-Increased sodium reabsorption water reabsorption,
raising blood volume
How is aldosterone regulated?
- If BP low more Renin made
- Decreased renal perfusion pressure (normally associated with decreased arterial BP)
- Increased renal sympathetic activity (direct to JGA cells)
- Decreased Na+ load to top of loop of Henle (macula densa cells)
How does renin work?
- Renin comes out of kidney
- Enzymes? convert angiotesingen (from liver) to angiotensin 1
- This is then covered to angiotensin 2 by enzyme ACE
- This stimulates vasoconstriction and directly tells adrenal gland to make aldosterone in zona glomerusa
How does angiotensin 2 make aldosterone?
Activation of the following enzymes Side Chain Cleavage 3 Hydroxysteroid dehydrogenase 21 hydroxylase 11 hydroxylase 18 hydroxylase
What is a summary of what aldosterone? does?
Controls blood pressure, controls sodium retention and lowers potassium
So what happens if you are stabbed or suddenly BP falls?
- Make renin
- Renin stimulates proaction of angiotensin 2
- This turns on these enzymes in adrenal gland to make aldosterone rapidly
- Therefore train sodium and so do not die from fall of BP
What are the metabolic effects of cortisol?
- peripheral protein catabolism
- hepatic gluconeogenesis
- increased blood glucose concentration
- fat metabolism (lipolysis in adipose tissue)
- enhanced effects of glucagon and catecholamines
What are the renal and cardiovascular effects of cortisol?
- excretion of water load
* increased vascular permeability
What are other physiological effects of cortisol?
- Normal stress response
- Weak mineralocorticoid effects
How is cortisol regulated ?
- ACTH (hormone) from pituitary gland
- Cortisol puts two steps of negative feedback so if too much will suppress ACTH in pituitary gland and precursor of ACTH (CRH) in the hypothalamus
- Negative feedback via circulation
What is the effect of ACTH on the adrenals?
Activation of the following enzymes Side Chain Cleavage 3 Hydroxysteroid dehydrogenase 21 hydroxylase 11 hydroxylase 18 hydroxylase
What is the rhythm of cortisol?
- Diurnal
- Up at 5am and peak 8:30 then goes down
- Circadian rhythm
What is Addisons disease?
- Thomas Addison (18th century)
1. Primary adrenal failure
2. Autoimmune disease where the immune system decides to destroy the adrenal cortex (UK)
3. Tuberculosis of the adrenal glands (commonest cause worldwide)
4. Pituitary starts secreting lots of ACTH and hence MSH
Why do patients with Addisons disease have a good tan?
- POMC is a large precursor protein that is cleaved to form a number of smaller peptides, including ACTH, MSH and endorphins
- Thus people who have pathologically high levels of ACTH may become tanned
What is the urgent treatment of addinosian crisis?
- Rehydrate with normal saline
- Give dextrose to prevent hypoglycaemia which could be due to the glucocorticoid deficiency
- Give hydrocortisone or another glucocorticoid
What happens during Addions disease?
- Increased pigmentation
- Autoimmune vitiligo may coexist
- No cortisol or aldosterone, so low blood pressure
What is a summary of Addions disease?
- Cortisol deficiency
- Aldosterone deficiency
- Salt loss
- Low blood pressure
- Eventual death
What is Cushing;s syndrome?
- Too much cortisol: metabolism changes and put on weight
- Can cause too much cortisol` tumour of adrenal: excess cortisol, tumour of pituitary: excess ACTH
- Occurs due to an excess of cortisol or other glucocorticoid
What are the clinical signs of Cushing’s syndrome?
- Thin skin
- Proximal myopathy
- Centripetal obesity (lemon on sticks)
- Diabetes, hypertension and osteoporosis
- Immunosuppression (reactivation of TB)
- Moon face
- Striae
What are the dour possible causes of Cushings syndrome?
- Taking steroids by mouth (common)
- Pituitary dependent Cushing’s disease (pituitary adenoma)
- Ectopic ACTH (lung cancer)
- Adrenal adenoma or carcinoma
What are catecholamines?
- Medulla derived from ectodermal neural crest
- Precursor for Adr & NA synthesis = tyrosine
- Catecholamines stored in cytoplasmic granules & released in response to ACh from preganglionic sympathetic neurones
What is the 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
