Discuss the urine formation process in human. Explain the structure of kidney.

The main excretory organ in human being is kidney that releases about 80% of liquid waste from the body. Urine formation occurs in the kidney in 3 parts- glomerular filtration, re-absorption and secretion. The afferent arteriole brings blood to the kidney and forms a bunch of capillaries in the Bowman’s capsule. Glomerular filtration occurs in the Bowman's capsule where glucose, salts, amino acids, urea get collected after filtration. Water and solutes that are smaller than proteins are forced into the renal tubule where reabsorption of water, glucose, amino acids and needed ions occurs and returns them back to the blood. Tubular secretion removes additional wastes from the blood and adds them to the filtrate. Further, water is removed from urine and returned to blood. Urine is sent to the collecting ducts.

Kidneys are bean-shaped organs located in the left and right of vertebrae column backside below stomach. Each kidney is enclosed in a renal capsule which is surrounded by the adipose tissue. Internally the kidney has the following parts- renal cortex, renal medulla, renal pyramids, renal columns and renal pelvis along with major and minor calyces. Kidney is the main excretory organ of excretion that releases about 80% of liquid waste from the body. Blood enters the kidney through renal artery and leaves the kidney through renal vein.