Adrenal gland

Question 1

What is the location of the adrenal gland?

Answer 1

• Close to pole of each kidney
• Level with 1st/2nd lumbar vertebrae
• Retroperitoneal
• Dorsal aspect of abdominal cavity

Question 2

Describe the vascular supply to the adrenal gland

Answer 2

• Supplied by: superior, middle & inferior suprarenal arteries, form a plexus beneath capsule. Cortical arteries & arterioles branch off into capillary beds in cortex
• Drained by: central medullary vein which anastomoses with vena cava/renal vein

Question 3

What areas are the adrenal glands split into?

Answer 3

1. Zona glomerulosa - cells arranged in distinct rods
2. Zona fasciculata - cells contain lipid droplets & arranged in cords
3. Zona reticularis - cells arranged irregularly

Question 4

Which 2 anatomically & functionally distinct endocrine glands are the adrenal glands comprised of?

Answer 4

Adrenal medulla & adrenal cortex

Question 5

Describe the adrenal medulla

Answer 5

• Extension of sympathetic NS - preganglionic fibres run straight to medulla without post fibre inbetween
• Secretes A directly into blood stream
• Secretes catecholamines

Question 6

What are the actions of catecholamines?

Answer 6

• Reinforces sympathetic NS during ‘fight or flight’
• Widespread effects - increase HR, vasoconstriction in skin & splanchnic bed, vasodilation to skeletal muscles, dilation airways, increase availabilty of glucose & catabolism of fats
• Day-to-day action - stimulate cellular K uptake

Question 7

Describe the adrenal cortex

Answer 7

• Secretes steroid hormones
• 3 classes of steroid hormones: mineralocorticoids, glucocorticoids, sex steroids

Question 8

What are the functions of mineralocorticoids?

Answer 8

• Main target organ is distal nephron
• Maintain high Na:K in ECF, promoting Na reabsorption & K secretion
• Similar actions in gut, salivary & sweat glands
• Exchange intratubular Na with extracellular K
• Essential for maintenance of blood pressure/volume
• e.g. Aldosterone

Question 9

What are the functions of glucocorticoids?

Answer 9

• Mobilise AA from skeletal muscle
• Stimulate AA uptake by liver
• Induce hepatic enzymes for gluconeogenesis

* cortisol required for normal hepatic glucose formation*

• Increase CHO synthesis & storage, decrease utilisation - causes hyperglycaemia
• Permissive role on actions of thyroxine & catecholamines, regard to lipolytic actions
• Inhibits normal inflammatory response

Question 10

State 2 disorders of adrenocortical function

Answer 10

1. Adrenocortical insufficiency (Addison’s disease)
2. Adrenocortical hyperfunction (Cushing’s disease)

Question 11

Explain adrenocortical insufficiency

Answer 11

• Deficiency of aldosterone secretion, often complicated by loss of cortisol secretion
• Causes Na wastage/K retention, dehydration, circulatory collapse, death
• Cortisol deficiency causes weakness, fatigue, hypoglycaemia
• Treatment - life long mineralocorticoid & glucocorticoid replacement therapy

Question 12

What are the 3 forms adrenocortical hyperfunction can present in?

Answer 12

1. adenoma (adrenal tumour) - secrete cortisol independantly of ACTH
2. non-pituitary ACTH or CRH secreting tumours
3. Excess pituitary production of ACTH

Question 13

What are the treatment options for adrenocortical hyperfunction?

Answer 13

• Adrenalectomy - bilateral, life long mineralocorticoid & glucocorticoid replacement therapy. Unilateral - fine
• Adrenal cytotoxic drugs - decrease adrenal capacity for cortisol secretion
• Competitive steroid inhibitors - block glucocorticoid biosynthesis & block aldosterone to spare K excretion