CBSE Class 10 Answered

The first step in urine formation is the filtration of blood, which is carried out by the glomerulus and is called glomerular filtration. 1100-1200 ml of blood is filtered by the kidneys per minute. The volume of the filtrate formed per day is about 180 litres per day, but the volume of urine finally released is only about 1.5 litres. This suggests that nearly 99 per cent of the filtrate has to be reabsorbed by the renal tubules. This process is called reabsorption. The tubular epithelial cells in different segments of nephron perform this either by active or passive mechanisms.