glomerulosa

Glomerulosa, in human anatomy, refers to the zona glomerulosa, the outermost layer of the adrenal cortex. It lies beneath the adrenal capsule and surrounds the adrenal medulla. Histologically, it is characterized by small, rounded clusters of pale-staining cells that form glomerulus-like arrangements.

The primary function of the zona glomerulosa is the production of mineralocorticoids, mainly aldosterone. Aldosterone acts on the kidneys to increase sodium reabsorption and potassium and hydrogen ion excretion in the distal tubules and collecting ducts, thereby helping to regulate extracellular fluid volume, blood pressure, and electrolyte balance.

Aldosterone secretion is regulated mainly by the renin-angiotensin-aldosterone system. Angiotensin II stimulates aldosterone synthesis; plasma potassium levels directly stimulate aldosterone release. Adrenocorticotropic hormone (ACTH) has a short-term, permissive effect but does not set baseline aldosterone production.

Developmentally, the zona glomerulosa is part of the adrenal cortex derived from mesoderm. It constitutes the outer cortical layer, distinct from the adjacent zones that produce glucocorticoids (zona fasciculata) and androgens (zona reticularis).

Clinical significance includes conditions of aldosterone excess or deficiency. Primary hyperaldosteronism (Conn's syndrome) results in hypertension, hypokalemia, and metabolic alkalosis, due to autonomous aldosterone production. Secondary hyperaldosteronism arises from increased RAAS activity in conditions such as renal, cardiac, or hepatic disease. Hypoaldosteronism, seen in adrenal insufficiency, can cause hyperkalemia, hyponatremia, and hypotension.

In relation to other adrenal zones, the zona glomerulosa is thinner and more compact than the fasciculata and reticularis, reflecting its specialized production of mineralocorticoids.