Define structure and function of nephron

The excretory units of the kidneys are called nephrons. Each kidney has a large number of nephrons packed close together.
Each nephron has a cup-shaped start called the 'Bowman's capsule' into which project a tuff of capillaries called 'Glomerulus'. The blood is brought into the kidney by the glomerulus. After the filtration in the Bowman's capsule, blood enters into the tubular part of the nephron where useful molecules like glucose, amino acids, salts, vitamins and a major amount of water etc. are selectively reabsorbed as urine flows along the tube. The final filtrate is finally drained into the ureters. The final waste contains water and nitrogenous wastes like urea, uric acid, etc.

Functioning of Nephron

1. Filtration: Filtration of blood takes place in Bowman’s capsule from the capillaries of glomerulus. The filtrate passes into the tubular part of the nephron. This filtrate contains glucose, amino acids, urea, uric acid, salts and a major amount of water.
2. Re-absorption: As the filtrate flows along the tubule useful substances such as glucose, amino acids, salts and water are selectively re-absorbed into the blood by capillaries surrounding the nephron tubule.
3. Urine: The filtrate which remains after re-absorption is called urine. Urine contains dissolved nitrogenous waste, i.e. urea and uric acid, excess salts and water. Urine is collected from nephrons by the collecting duct to carry it to the ureter.