The adrenal glands Flashcards
What does the adrenal cortex arise from?
Intermediate mesoderm
What does the adrenal medulla arise from?
Neural crest (chromatin cells)
What are the layers of the adrenal cortex?
- Zona glomerulosa
- Zona fasciculata
- Zona reticularis
Role of zona glomerulosa
- Mineralocorticoids e.g. aldosterone
- Controlled by renin angiotensin
- Electrolyte and fluid homeostasis
Role of the zona fasciculata
- Glucocorticoids e.g. cortisol
- Secretion controlled by ACTH
- Carbohydrate, lipid and protein metabolism
What is the role of the zona reticularis?
•Sex steroids - androgens
What is the blood supply of the adrenal Cortex?
- Superior, middle and inferior adrenal arteries
* Cortex receives short cortical arteries that run in parallel with the cords of cells to the medulla
What is the blood supply of the adrenal medulla?
- Blood draining from the cortex (containing adreno-corticosteroid which influence the production of adrenaline by the medullary cells)
- Fresh arterial blood in long cortical arteries
Describe the short term stress release
- Catecholamines are released from the adrenal medulla
- Increased heart rate
- Increased blood pressure
- Liver converts glycogen to glucose and releases glucose to blood
- Dilation of bronchioles
- Changes in blood flow patterns leading to decreased digestive system activity and reduced urine output
- Increased metabolic response
Describe the long term stress response
- Mineralocorticoids: Retention of sodium and water by the kidneys -> increased blood volume and blood pressure
- Glucocorticoids: Proteins and fates are converted to glucose or broken down for energy -> increased blood glucose -> suppression of the immune system
What are the actions of cortisol?
In the muscle cell:
• inhibits the uptake of glucose
•Less protein synthesis occurs so there is a net proteolysis so increased free amino acids (which can be used in glujconeogeneis
In the fat cell:
•Inhibits the uptake of glucose
•Decreased lipogenesis
•Net lipolysis, increased free glycerol (which can be used in gluconeogenesis)
In the liver cell
•Increased gluconeogenesis
•Increased glucose
What causes Cushing’s disease?
Excess of glucocorticoids: •ACTH- releasing pituitary tumour •Ectopic ACTH releasing tumour •Tumour of the adrenal cortex •Administration of pharmacological doses of glucocorticoid drugs
What are the mechanisms controlling aldosterone secretion?
Increased aldosterone release stimulated by:
•Increased ACTH
•Increased plasma K+
•Angiotensin II (main)
Reduced release by:
•aldosterone causes increased potassium excretion, decreasing the plasma K+
•Negative feedback inhibiting renin secretion by the kidney reducing the conversion of angiotensinogen to angiotensin I, resulting in reduced angiotensin II
Describe the structure of the juxta-glomerular apparatus
- The afferent arteriole enters the capsule, glomerular capillaries are surrounded by the endothelial cells surrounded by podocytes
- The distal tubule comes into close contact with the afferent and efferent arteriole
- The macula densa cells of the distal tubule sense the sodium chloride content
What is the role of the macula densa cells?
They sense the sodium chloride concentration of the tubular fluid, if there is a decrease, they start to synthesise prostaglandins which interact with the modified smooth muscle cells and cause the release renin
