3.1 Structure and Function of the Adrenal Glands

Question 1

Where are the adrenals relative to the peritoneum (and why does this make sense)? What ribs do they align with on either side (and why does this make sense)? Describe their position relative to the kidneys in all three axes

Answer 1

• Adrenals are retroperitoneal (same as kidneys)
• Left: 11th-12th rib, whereas right is 12th rib (pushed down by liver)
• Adrenals are superior (riding), and slightly anteromedial to the kidneys

Question 2

Describe the origin of the three suprarenal arteries. These arteries supply the ____.

Answer 2

• Superior suprarenal: inferior phrenic
• Middle suprarenal: aorta
• Inferior: renal artery

These supply the adrenal glands.

Question 3

Describe venous drainage of the adrenals on both sides

Answer 3

• Left: drains into left adrenal vein, which drains into left adrenal vein (pressure needed to cross pulsating aorta), and then the IVC
• Right: doesn’t cross aorta; can drain directly into the right suprarenal vein, and then the IVC

Question 4

Describe the structure of the vasculature in the adrenals. Where else in the body’s endocrine system do we see this?

Answer 4

• Two capillary networks between arteries and veins, one superficial, and one deep
• This is similar to the two capillary networks that we see in the anterior pituitary, allowing for the hypophyseal portal system and then the release of hormones into the vasculature

Question 5

Where do the cells that become the adrenal medulla migrate from during embyronic development?

Answer 5

• Neural crest
• Think back to neural tube formation; this makes sense

Question 6

When it occurs outside of the adrenal glands, a phaeochromocytoma is called…

Answer 6

Paraganglioma.

Question 7

Which enzyme is involved in converting 17-OH-progesterone into mineralocorticoids and glucocorticoids? Therefore, what can happen when it is deficient? What condition is often caused by this?

Answer 7

• Enzyme is called 21 hydroxylase
• When deficient, more androgens are produced; can lead to excess
• This condition is the basis for the majority of cases of CAH

(Remember Ben Canny)

Question 8

Which amino acid are catecholamines derived from? What other class of hormones is derived from this amino acid?

Answer 8

• Derived from tyrosine
• Same as thyroid hormones

Question 9

Describe the 5 steps in the catecholamine pathway

Answer 9

1. Tyrosine
2. L-Dopa
3. Dopamine
4. Adrenaline
5. Noradrenaline

Question 10

Why isn’t adrenaline released from postanglionic sympathetic fibres? After all, it’s released from chromaffin cells, which are kind of the same thing, right?

Answer 10

The enzyme that adds a methyl to NA to make it Adrenaline (called PNMT); is present in high conc in chromaffin cells, but this is not the case in sympathetic nerves.

Question 11

What are the main controllers of aldosterone secretion? What is NOT?

Answer 11

• Not ACTH
• Regulated by K+ conc and Ang II conc