Question

The diagram given shows a section of a human kidney. Study the diagram carefully and answer the questions that follow:
(i) Label the parts numbered 1 to 4.
(ii) Why does part '2' have a striped appearance?
(iii) What is the fluid that passes down part '4'? Name the main nitrogenous waste present in it.
(iv) Mention the structural and functional units of kidneys.
(v) Name the two major steps in the formation of the fluid mentioned in (iii).

Answer 1

Hint: The kidney is an important excretory organ in our body. It helps in removing the nitrogenous wastes from the blood and forms urine. The blood undergoes several filtrations under high pressure through the kidney and forms urine. The reabsorption of the useful ions takes place in the kidney tubules and the wastes are eliminated in the form of urine.

Complete answer:
To solve this question, we must know about the structure and function of the kidney.
i). The different parts shown in the kidney are
1. Cortex- It is the outermost portion of the kidney. It contains glomerulus and convoluted tubules. Ultra-filtration takes place here.
2. Medulla- It is the innermost part of the kidney. It regulates the concentration of urine.
3. Pelvis- It acts as a funnel for urine flowing to the ureter.
4. Ureter- It is the tube which carries the urine from kidney to the urinary bladder.
ii). The medulla appears to be stripped in appearance because it contains the renal tubules which are the structural and functional unit of the kidney. These tubules are highly coiled and microscopic in appearance.
iii). The fluid that passes down through the ureter is the urine. The main nitrogenous waste present in it is urea. Urea is formed as a result of breakdown of proteins by the liver.
iv). The structural and functional unit of the kidney is the nephrons. It contains glomerulus, proximal convoluted tubule, distal convoluted tubules, loop of henle.
v). The urine is majorly formed by two important steps- Ultrafiltration which takes place in the glomerulus and reabsorption which takes place in renal tubules (proximal convoluted tubule).

Note:
I) Ultrafiltration- It occurs in glomerulus. The blood under high pressure passes through the capillaries filtering many solutes and water and wastes.
II) Reabsorption is the process of movement of water and other important solutes from the renal tubule to the blood. Water, glucose, proteins and important amino acids are reabsorbed in the renal tubules.