CBSE Class 10 Science 2020 · Paper 31/1/1 · Question 27(b)

(a) The excretory system of human beings consists of a pair of kidneys, a pair of ureters, a urinary bladder and a urethra. (b) Urine is produced in the nephrons, the filtration units of the kidneys. Each nephron has a cup-shaped Bowman's capsule containing a bunch of capillaries called the glomerulus. Blood containing nitrogenous wastes is filtered in the glomerulus, and the filtrate collects in Bowman's capsule. As the filtrate flows along the tubule of the nephron, useful substances such as glucose, amino acids, salts and a major amount of water are selectively reabsorbed into the blood capillaries around it. The fluid that remains is urine; the urine formed in each kidney passes through the collecting ducts into the ureter and is carried to the urinary bladder, where it is stored until it is passed out through the urethra.