Renal System — Kidney Function

The kidney's functional unit is the nephron.

Nephron parts and functions:

Glomerulus — filtration of blood; produces filtrate

Bowman's capsule — collects filtrate

Proximal convoluted tubule (PCT) — reabsorbs ~65% of water, Na⁺, glucose, amino acids

Loop of Henle — creates concentration gradient in medulla; descending loop permeable to water; ascending loop permeable to Na⁺

Distal convoluted tubule (DCT) — regulated reabsorption of Na⁺ (aldosterone), Ca²⁺

Collecting duct — water reabsorption controlled by ADH

Regulation:

ADH (vasopressin) — increases water reabsorption in collecting duct → concentrated urine

Aldosterone — increases Na⁺ (and water) reabsorption in DCT → raises blood pressure

Atrial natriuretic peptide (ANP) — decreases Na⁺ reabsorption → lowers blood pressure

GFR (glomerular filtration rate): ~125 mL/min in healthy adults. Key indicator of kidney function. Decreases with kidney disease.

Reference:

Wikipedia: Kidney

https://en.wikipedia.org/wiki/Kidney