Question

The process of urine formation in kidneys includes which one of the following?
a. Replication
b. Glomerular filtration
c. Respiration
d. Perspiration

Answer 1

Hint: Kidneys are the organ of the excretory system. The nephron, consisting of the renal corpuscle and renal tubule, is the structural and functional unit of the kidney. As the renal tubule processes and carries away the filtered fluid, the renal corpuscle is the initial filtering portion of the nephron.

Complete answer:
> Option (A) is incorrect. Replication is the process by which DNA gets replicated into two daughter DNA strands. It takes place within the cell’s nucleus.

> Option (B) is correct. The process of urine formation in kidneys is a three-step process i.e., filtration in the glomerulus, reabsorption of useful nutrients in the renal tubule, and secretion of certain ions and some water from the capillaries into the renal tubule. The filtration process in the glomerulus is also known as glomerular filtration i.e., an ultrafiltration process.

> Option (C) is incorrect. Respiration is the process of exchange of gases i.e., oxygen and carbon dioxide from and to the environment, respectively. This process is carried out by the lungs present in the thoracic cavity of humans.

> Option (D) is incorrect. Perspiration, also known as sweating, is the production of fluids that are secreted by the sweat glands present in the skin of the mammals.

Hence, the correct answer is option (B).

Note: Urine formation in the kidneys is a three-step method i.e., glomerular filtration, reabsorption, and secretion. These are the processes that ensure that only waste materials and excess water is excreted out of the body while the remaining useful substances are again reabsorbed after the filtration process. Urine, thus produced contains $95\%$ water and $5\%$ waste products.