Which statement about capillary filtration is true?

Which statement about capillary filtration is true?

• A. Filtration is driven by capillary hydrostatic pressure
• B. Filtration is driven by lymphatic pressure
• C. Reabsorption is driven by capillary hydrostatic pressure
• D. Net movement is independent of hydrostatic pressure

Answer: (A)

Movement of fluid across capillaries is governed by Starling forces, with the outward push from capillary hydrostatic pressure driving filtration of fluid from blood into the interstitial space. This means that where capillary pressure is higher, more fluid is pushed out, forming filtrate. The return of fluid to the bloodstream—reabsorption—is mainly driven by the osmotic (oncotic) pressure created by plasma proteins drawing water back in, not by lymphatic pressure. The lymphatic system helps drain excess interstitial fluid but does not set filtration. Because filtration depends on the capillary hydrostatic pressure, the statement is correct.

Movement of fluid across capillaries is governed by Starling forces, with the outward push from capillary hydrostatic pressure driving filtration of fluid from blood into the interstitial space. This means that where capillary pressure is higher, more fluid is pushed out, forming filtrate. The return of fluid to the bloodstream—reabsorption—is mainly driven by the osmotic (oncotic) pressure created by plasma proteins drawing water back in, not by lymphatic pressure. The lymphatic system helps drain excess interstitial fluid but does not set filtration. Because filtration depends on the capillary hydrostatic pressure, the statement is correct.