Adrenal Glad
Anatomy : The paired Adrenal Glands superior to each of the two kidneys have a flat pyramid shape.
The adrenal glands have 2 structurally distinct parts:
Adrenal Cortex – the outer part, 80-90% of the size, produces steroid hormones absolutely essential for life Adrenal Medulla – the inner part, remaining 10-20% of the gland, produces catecholamine hormones not essential for life
The Adrenal Cortex
Secretory Cells, Hormones, Target & Function:
1) Zona Glomerulosa : the outer most layer that secrete hormones called Mineralcorticoids (they affect mineral homeostasis). They target the kidneys. • Aldosterone is the major hormone • Regulates Na+ and K+ ions • Adjust blood pressure and blood volume • Promotes excretion of H+ in the urine thereby removing acids from the body and preventing acidosis. 2) Zona Fasciulata : the middle and widest layer that secrete Glucocorticoids (they affect glucose homeostasis). They target all body cells. • Regulate metabolism and resistance to stress and include: Cortisol (hydrocortisone), Corticosterone, and Cortisone . Cortisol is the most abundant (~95% of all glucocorticoid activity). • Protein breakdown : increased protein breakdown = increased AAs in the bloodstream = synthesis of NEW proteins or for ATP production. • Glucose formation : liver cells convert certain AAs or lactic acid to glucose, which neurons or other cells use for ATP production. This process is called Gluconeogenesis. • Lipolysis : the breakdown of triglycerides = release of fatty acids from adipose tissue into the blood. • Resistance to Stress : additional glucose by the liver provides a“ready” source of ATP to combat stress. Glucocorticoids also make blood vessels more sensitive to other hormones that cause vasoconstriction (which raises blood pressure). This is an advantage during extreme blood loss which cause a decrease in blood pressure. 3) Zona Reticularis : the inner zone that synthesize Androgens (steroid hormones that have masculinizing effects). They target the reproductive tissues. • The number of androgens secreted by males is minimal due to the release of testosterone secreted during puberty but play a role in sperm production.
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