Question

The given diagram represents a nephron and its blood supply. Study the diagram and answer the following questions.

(d) Name the two main stages of urine formation.

Answer 1

Urine formation:

1. Nephrons are the basic structural and functional unit of the kidney. It filters the blood and helps in the elimination of nitrogenous wastes from the body.
2. The formation of urine occurs in two main steps - ultrafiltration and selective reabsorption.

Ultrafiltration:

1. Ultrafiltration is a type of filtration which occurs under high pressure in the glomerulus.
2. In this process, the blood passes through the glomerulus under high pressure. This facilitates the filtration of blood plasma through the thin, porous epithelium of the glomerulus and Bowman capsule’s wall into the capsule space.

Selective Reabsorption:

1. Reabsorption refers to the absorption of water, glucose, amino acids, salts, and other useful substances from the glomerular filtrate back into the bloodstream.
2. About 99% of glomerular filtrate is reabsorbed in the proximal convoluted tubule, the loop of Henle, the distal convoluted tubule, and collecting ducts of the nephrons.