Urine formation takes place in three steps, viz. glomerular filtration, reabsorption and collection:
- Glomerular Filtration: The tuft of capillaries inside bowman’s capsule is called glomerulus. It is connected with two types of arterioles. Afferent arteriole take blood to glomerulus and efferent arteriole take blood away from glomerulus. The lumen of efferent arteriole is less than that of afferent arteriole. This creates high pressure inside glomerulus and thus blood is filtered under high pressure. Glucose, amino acid, urea, etc. are filtered from blood and sent to bowman’s capsul
- Reabsorption: The glomerular filtrate contains high quantity of water. This water is reabsorbed as glomerular filtrate passes through convoluted tubules. Some salts are also reabsorbed. Reabsorption helps in reducing the volume of urine.
- Collection: After reabsorption, urine is formed. It passes through collecting duct and finally is stored in urinary bladder.
- Structure of Kidney: Kidney resembles like kidney beans and is dark brown in colour. There is a constriction in the middle and it is called hylum. There is a funnel shaped pelvis on the inner side of hylum. The outer part of kidney is called cortex and the inner part is called medulla. Each kidney has numerous filtering units called nephrons.
