Reabsorption is the process by which water is reabsorbed from the tissues back into the venous end of the blood capillary.

• A. Water moving from tissues back into the arterial end of the capillary
• B. Water moving from tissues back into the venous end of the blood capillary
• C. Water moving into the lymphatic capillaries
• D. Water being secreted into the interstitium

Answer: (B)

Reabsorption is the movement of fluid from the interstitial space back into the capillary, mainly on the venous end. This happens because capillary oncotic pressure (from plasma proteins) remains relatively high while capillary hydrostatic pressure has fallen as blood moves along the vessel. The higher oncotic pull draws water back into the capillary, so most reabsorption occurs toward the venous end. A portion of the fluid that isn’t reabsorbed is taken up by the lymphatic system. The other options describe water exiting into interstitial space, entering lymphatics, or moving into arteries, which are not reabsorption.