The kidneys in human beings are a part of the system for
  1. nutrition.
  2. excretion.
  3. respiration.
  4. transportation.

AcademicBiologyNCERTClass 10

Correct Answer: (c) Excretion


The most important job done by the kidneys is to filter the waste out of the blood and expel it as urine. They also help in maintaining the water level and various essential minerals in the body.

Kidneys excrete waste products like urea and other soluble salts and excess fluid from the blood. The names of tubes that connect the kidneys to the bladder are known as ureters. The urinary bladder is a hollow muscular organ that helps to collect and store urine from the kidneys.

The nephron is the basic structural and functional unit of the kidney. Each nephron contains a renal corpuscle and a renal tubule. The renal corpuscle consists of capillaries called the glomerulus, which is enclosed by a capsule called Bowman’s capsule. First, blood containing waste like urea is filtered by the glomerulus and this is called glomerular filtration.

Urine formation involves three main processes: glomerular filtration, tubular reabsorption, and tubular secretion, which take place in different parts of the nephron.

During filtration, the substances like glucose, salts, amino acids, urea, water, etc. present in the blood pass into Bowman's capsule and then enter the renal tubule of the nephron where the necessary materials are reabsorbed into the blood through blood capillaries and only waste substances like urea and excess water remain behind in the tubule.

Now, the nephron carries the urine into the collecting tubule of the kidney, from where it is carried to the ureter. From the ureter, the urine passes into the urinary bladder, which stores the urine until it is forced out of the body, through an opening known as the urethra.


Updated on 10-Oct-2022 13:19:00