L7 Adrenal Glands

Question 0

Why is there a rich blood supply to adrenal gland?

Answer 0

• to take the hormones away, circulating the body (5ml/min)

Question 1

What are the 3 majr structural components of adrenal glands?

Answer 1

• capsule, outer cortex and inner medulla

Question 2

What is the blood supply to adrenal glands?

Answer 2

• Arterial: inferior phrenic artery branches off and supply the cortex. And then continues onwards and merge with medulla arterial blood supply
• Venous: there is only one vein draining deoxygenated blood away from adrenal gland -> because glucocorticoids produced in zona fasiculata (namely cortisol) has to travel to medulla to promote synthesis of adrenaline

Question 3

What does zona glomerulosa produce?

Answer 3

• mineralcorticoids, eg. aldosterone (only produced in adrenal glands)
• Made up of 15% of cortex

Question 4

What does zona fasciulata produce?

Answer 4

• glucocorticoids, eg cortisol and small amounts of androgens
• make up largest part of cortex ~75%
• regulated by ACTH

Question 5

What does zona reticularis produce?

Answer 5

• androgens and small amount of glucocorticoids
• make up 10% of cortex
• regulated by ACTH

Question 6

What is the proportion of cortex and medulla in adrenal glands?

Answer 6

• 90% of cortex and 10% of medulla

Question 7

Where are the synthesis of catecholamine hormones?

Answer 7

• at medulla of adrenal gland by chromatin cells
• mostly adrenaline and some noradrenaline

-synthesis of adrenaline: phenylalanine -> p-tyrosine -> Dopa -> dopamine -> Na -> A

Question 8

What type of innervation stimulates chromaffin cells?

Answer 8

• pre-ganglionic neurotransmitter (ACH) stimulates calcium mediated exocytosis
• post-synaptic ganglion contains modified neurones (not axons)

Question 9

What stimulates the release of catecholamines in the circulation?

Answer 9

• sympathetic system stimulates the release of catecholamines

Question 10

Does adrenaline or noradrenaline have longer half life and what is the level circulating in blood?

Answer 10

• Adrenaline and Noradrenaline both bound to albumin
• Adrenaline (20-50ng/ml) has longer half life than noradrenaline (100-350ng/ml) so there is a lower level of adrenaline present in blood as they are more potent
• Adrenaline are made by adrenal medullary chromaffin cells whereas noradrenaline is mostly made from post-ganglionic sympathetic neurones
• Max level of adrenaline can be >15000 ng/ml at cardiac arrest

Question 11

What are the functions of adrenal medullary catecholamines?

Answer 11

• adrenaline is the strongest agonist for both alpha and beta adrenoceptors
• it induces flight or fight response, bring about CVS changes, stimulates stress response (in short term) and promote catabolic effects

Question 12

What stimulates the release of glucocorticoids?

Answer 12

• it is activated by hypothalamo-pituitary adrenal axis so there is an increase in CRH which acts on anterior pituitary and releases ACTH.
• ACTH acts on adrenal cortex to release cortisol

Question 13

What are the functions of glucocorticoids? (6)

Answer 13

• metabolic: increase break down of glycogen
• cardiovascular
• immunologic: suppress T cells = anti-inflammatory
• homeostatic: regulate calcium excretion in kidneys
• musculoskeletal
• arousal & mood: promote depression in long term
• mainly promotes catabolism