If Plasma Osmolarity Increases,as in Dehydration or the Infusion of Mannitol

Question

If plasma osmolarity increases,as in dehydration or the infusion of mannitol (a sugar solution),
A) filtration rate increases.
B) fluid is forced out of the capillary into the interstitium.
C) fluid is "pulled" into the capillary from the interstitium.
D) plasma proteins diffuse out of the capillary into the interstitium.

Accepted Answer

An increase in plasma osmolarity stimulates the movement of fluid out of the interstitium and into the capillary, a process known as osmosis. This occurs because the higher osmolarity of the plasma creates a concentration gradient that "pulls" water molecules into the capillary where the osmolarity is lower. Therefore, fluid is "pulled" into the capillary from the interstitium.