BRIAN EVANS / SCIENCE PHOTO LIBRARY BRIAN EVANS / SCIENCE PHOTO LIBRARY
Kidney nephron. Artwork of a healthy human kidney nephron. Each of the kidneys, which excrete urine and regulate blood and electrolyte balance, contains about a million of these units. Fluid is filtered from the blood of the arteriole (red, top right) by the ball-like glomerulus in the Bowman's capsule (light brown sphere, upper centre). The fluid collects in the proximal tubule (light brown) below. Nearly all water and salts are reabsorbed from this tubule and its straight section, the U-shaped loop of Henle (lower left), into the blood. The remaining fluid, urine, travels along the distal tubule and into the collecting duct (bottom left).
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