question_answer 32)

Describe the structure and functioning of nephrons.

Answer:

Kidney is made up of large number of excretory units called nephrons. The nephron has a cup-shaped bag at its upper end which is called Bowman's capsule. The lower end of Bowman's capsule is a U-shaped tube called tubule. The Bowmans capsule and tubule together make the nephron. The one end of tubule is connected to Bowman's capsule and its other end is connected to a urine-collecting duct of the kidney. The Bowman's capsule contains a bundle of blood capillaries which is called glomerulus. One end of glomerulus is attached to renal artery which brings the blood containing urea waste into it. The other end of glomerulus comes out of Bowman's capsule, blood capillaries surround the tubule and finally joins a renal vein. Functioning of Nephron The function of glomerulus is to filter the blood passing through it. All small molecules like glucose, water, amino acids, minerals etc., (except the blood cells and proteins) pass through it. This is called ultrafiltration. As the filtrate move down the tubule, the useful substances like glucose, amino acids and most of the water are reabsorbed by the capillary around the tubule, but the waste material remains like urea remains in tubule. This liquid is called urine. The nephron carries urine into the collecting duct of kidney, from where it is carried to the ureter.