Adrenals and their Hormones 8 Flashcards
Describe the rough anatomy of the Adrenals
They are located at the superior pole of the kidneys. They each have their own capsules and have many arteries supplying them but only one vein each. The right adrenal vein drains into the IVC and the left adrenal vein drains into the renal vein.
Describe Specific anatomy of the Adrenals
Comprised of a medulla and a cortex. The cortex produces corticosteroids while the medulla produces catecholamines
What are the sections of the cortex (from medulla out)?
Zona Reticularis
Zona Fasciculata
Zona Glomerulosa
How does blood get to the various zones?
- Flows through the cells in each zones from the exterior of the gland
- There are some vessels which flow through the cortex to get to the medulla
What is the medulla made of?
CHROMAFFIN CELLS and therefore associated to the produced catecholamines
What type of hormone does the cortex produce?
Steroids (therefore they are corticosteroids)
What does the medulla produce?
Catecholamines:
- Adrenaline (80%)
- Noradrenaline (20%)
- Dopamine (V.small amounts)
What does the cortex produce?
Cortiocsteroids:
- Mineralocorticoids = aldosterone
- Glucocorticoids = Cortisol
- Sex Steroids = androgens/oestrogens
Where is aldosterone produced?
Zona Glomerulosa
What are Cortisol and androgens/oestrogens produced?
Zona Fasciculata and Reticularis
What are adrenal cortical hormones synthesised from?
Cholesterol
Describe Cortisol Synthesis
1) Cholesterol
2) Pregnenolone
3) 17alpha-pregnenolone
4) 17alpha-progesterone
5) 11-deoxycortisol
6) Cortisol
Describe Aldosterone Synthesis
1) Cholesterol
2) Pregnenolone
3) Progesterone
4) 11-deoxycorticosterone
5) Corticosterone
6) Aldosterone
Describe Sex hormone Sythesis
1) Cholesterol
2) Pregnenolone
3) 17alpha-pregnenolone
4) Dehydroepiandrosterone
5) Androstenedione
6) Testosterone
Then either:
- Oestrodiol
- Dihydrotestosterone
What is the precursor to oestrogens?
Androgens
Describe Cortisol Transport
- Corticosteroid Binding Globulin (CBG) (80%)
- Albumin (10%)
- Bioactive (10%)
Describe Aldosterone Transport
- CBG (15%)
- Albumin (45%)
- Bioactive (40%)
When is cortisol released?
It is released at different times of the day (more in the morning). It is also released in pulses (pulsatile rhythm) on top of circadian rhythm
What receptor does aldosterone act on?
Mineralocorticoid receptor
What does Cortisol act on?
Mineralocorticoid and Glucocorticoid Receptors
How do tissues prevent Cortisol acting on Mineralocorticoid Receptors?
Some tissues have enzymes (kidney) that converts bioactive Cortisol to Cortisone (inactive). This enzyme is 11b-hydroxysteroid dehydrodgenase 2 (11bhsb2). This enzyme is present in the kidneys and the placenta
What is the action of Aldosterone?
- STIMULATE NA+ RE-ABSORPTION in the distal convuluted tubule and cortical collecting duct.
- STIMULATES K+ AND H+ SECRETION in the distal convuluted tubule and the collecting duct. This is for pH regulation of blood.
What is Aldosterone the end product of ?
Renin-Angiotensin System
Where is Renin released?
In the nephron, Macula Densa cells on the distal convuluted tubule sense Na+ concentration. These are in close proximity to the granular cells that line the afferent arteriole. These cells communicate and cause the granular cells to release the renin.
