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How do the kidneys remove wastes from the blood?
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The kidneys remove waste from the blood through the action of approximately 1,000,000 functional units called nephrons. This process involves three primary mechanisms:
- Glomerular Filtration: Blood enters the glomerulus, a cluster of capillaries enclosed within Bowmanâs capsule. Fluid and waste products are filtered out of the blood and into the nephron tubule.1
- Tubular Reabsorption: As the filtrate moves through the tubule, the body selectively reabsorbs essential substancesâsuch as water, glucose, and various saltsâreturning them to the bloodstream to maintain internal balance.12
- Tubular Secretion: The kidneys actively or passively transport additional waste products, such as uric acid, potassium, and hydrogen ions, from the peritubular capillaries directly into the filtrate.3
Through these steps, the kidneys eliminate metabolic end products like urea and creatinine while regulating the body's water, electrolyte, and acid-base balance. The final product, urine, is then conveyed to the renal pelvis for excretion.241