The nephron is the microscopic functional filtering unit of the kidney. Each nephron filters blood, recovers useful substances, and helps turn the remaining waste and excess water into urine.
A nephron begins with the glomerulus, a tuft of tiny blood vessels enclosed by Bowman’s capsule. Pressure pushes water and small dissolved molecules into the nephron while retaining most blood cells and large proteins. The filtrate then travels through a tubule, where the body reabsorbs needed water, glucose, salts, and other substances and secretes additional wastes.
The nephron is therefore more than a simple sieve. Its tubule adjusts the composition and concentration of urine, helping regulate blood volume, electrolytes, acid-base balance, and blood pressure. Hormones such as antidiuretic hormone and aldosterone influence how much water and sodium the tubule returns to the bloodstream.
Each human kidney contains roughly a million nephrons, although the number varies considerably between people. The glomerulus performs the initial filtration, but the complete nephron carries out the broader work of maintaining the body’s internal chemical balance.