Test: Mechanism of Concentration of the Filtrate (NCERT) - NEET MCQ

Bowman's capsule  - It contain tuft of capillaries (i.e., Glomerulus) and filters out the waste from the blood by the process of Glomerulus filtration. DCT - It helps in selectively reabsorb sodium, chlorine, potassium, calcium ions and water. Henle's loop - It helps in concentration of urine. PCT - It helps in the absorption majority of ions like - Na+ and K+.

The counter current mechanism in loop of Henle and vasa recta, helps in maintaining an increasing osmolarity of the interstitial fluid i.e. form 300 mOsmoL^-1 in the cortex is about 1200 mOsmolL^-1 in the inner medulla. This gradient is mainly caused by NaCl and urea. This gradient thus helps in easy reabsorption of water from the filtrate in the collecting duct so as to produce hyperosmotic urine.

As the urine passes through the descending limb it becomes hypertonic, as descending limb is more permeable to water and less permeable to sodium ions.
The filtrate becomes hypotonic as ascending limb is less permeable to water and more permeable to sodium ions.
The statement 1 is correct but the statement 2 is incorrect.

To match the columns correctly:

- PCT (Proximal Convoluted Tubule): Responsible for the reabsorption of 70-80% electrolytes from the filtrate.
- DCT (Distal Convoluted Tubule): Involves the maintenance of concentration gradient in the medulla.
- Loop of Henle: Part of the counter-current mechanism crucial for concentrated urine formation.
- Counter-current mechanism: Essential for the maintenance of the concentration gradient in the medulla.
- Renal corpuscle: Primarily involved in the filtration of blood.

Therefore, the correct answer is:
- A: PCT - (iii), DCT - (v), Loop of Henle - (i), Counter-current mechanism - (v), Renal corpuscle - (ii).

Sodium chloride (NaCl) is primarily transported by the ascending limb of Henle's loop in the process of concentrating urine in mammals. This transportation of NaCl, along with the exchange mechanisms with the vasa recta, plays a crucial role in establishing and maintaining the osmolarity gradient necessary for urine concentration within the nephron.