Q. Describe the structure and functioning of nephrons.
Nephron is the filtration unit of kidney. It consists of a tubule which is connected with collecting duct at one end and a cup – shaped structure at the other end.
This cup-shaped structure is called ‘Bowman’s capsule’. Every Bowman’s capsule contains a cluster of capillaries, called ‘Glomerulus’, within the cup – shaped structure. The blood enters into Glomerulus through afferent arteriole of renal artery and leaves it through efferent arteriole.
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.
The amount of water re-absorbed depends on the need of the body and also on the amount of wastes to be excreted.
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.