Q. During urine formation, which of the following processes create high osmotic pressure in the uriniferous tubule?
A) Active $Na^{+}$ absorption, followed by absorption of $Cl^{-}$
B) Active $Cl^{-}$ absorption, followed by absorption of $Na^{+}\$
C) Active secretion of $Na^{+}$ into efferent arteriole followed by absorption of $Cl^{-}$ into efferent renal arteriole
D) Active secretion of $Cl^{-}$ and absorption of $Na^{+}$ into efferent renal arteriole
Explanation
Osmotic pressure is a measure of tendency to take in water by osmosis. During urine formation, approximately two-thirds of the $NaCl^{-}$ and water filtered into Bowman’s capsule is immediately reabsorbed across the walls of proximal convoluted tubule. This reabsorption is driven by active transport of $Na^{+}$out of the filtrate and into surrounding peritubular capillaries. $Cl^{-}$follows $Na^{+}$passively because of electric attraction and water follows them both because of osmosis.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.