Question

question 44 (1 point)
which situations affect the re - absorption of water in the collecting duct of a nephron?
i. the presence of a hypertonic interstitial fluid
ii. the presence or absence of adh
iii. the active transport of water
iv. an osmotic gradient across the duct membrane
i and ii only
iii and iv only
i, ii, and iv only
ii, iii, and iv only

Explanation:

• I: Hypertonic interstitial fluid creates an osmotic gradient that drives water re - absorption from the collecting duct.
• II: Antidiuretic hormone (ADH) increases the permeability of the collecting duct to water. When ADH is present, more water is re - absorbed.
• III: Water re - absorption in the collecting duct is mainly through osmosis (passive transport), not active transport.
• IV: An osmotic gradient (such as that created by hypertonic interstitial fluid) is essential for water re - absorption from the collecting duct.

Answer:

C. I, II, and IV only