Question

The process of tubular secretion in nephron takes place in
A. Glomerulus
B. Proximal convoluted tube
C. Loop of Henle
D. Both B and C

Answer 1

Excretion is the process of removal of harmful metabolic waste from the body of an organism. Urine formation occurs in the kidneys. It involves three processes; glomerular filtration, tubular reabsorption, and tubular secretion.

Complete answer:
Kidneys are the major excretory and osmoregulatory organs of vertebrates. The human excretory system consists of a pair of kidneys, a pair of ureters, a urinary bladder, and a urethra.
The tubular secretion occur as under-
1. Creatinine, hippuric acid, and foreign substances (pigments, drugs including penicillin) are actively secreted into the filtrate in the PCT from the interstitial fluid. Hydrogen ions, and ammonia (N$H_3$) is also secreted into the PCT.
2. Potassium, hydrogen, N$H_4^+$, and HC$O_3^-$ ions are secreted by active transport, into the filtrate in the DCT.
3. Urea enters the filtrate by diffusion in the thin region of the ascending limb of Henle's loop.
4. It occurs mainly by active transport.
So, the correct answer is option D-Both B and C

Additional information :
A nephron is a unit of structure and function in a kidney. A nephron is a long tubule differentiated into four regions having different anatomical features and physiological roles: Bowman's capsule, proximal convoluted tubule (PCT), loop Henle and distal convoluted tubule (DCT). The latter opens into the collecting ducts.

Note: An infection in the kidney, injury to the kidney, or restricted blood flow can damage the kidneys and they stop working. Urea and other wastes collect in the blood and can cause even death if untreated.