Describe the capillary hydrostatic pressure gradient from arterial to venous ends.

• A. Capillary hydrostatic pressure is higher at the arterial end, promoting filtration; it declines along the capillary, aiding eventual reabsorption or lymphatic drainage at the venous end.
• B. Capillary hydrostatic pressure is higher at the venous end, promoting filtration.
• C. Hydrostatic pressure is constant along the capillary.
• D. There is no hydrostatic pressure gradient in capillaries.

Answer: (A)

Capillary hydrostatic pressure is the force within the capillary that pushes fluid out into the surrounding tissue. It is highest at the arterial end of the capillary and then declines as blood moves toward the venous end. This gradient means fluid is filtered out of the capillary at the arterial end, delivering water and solutes to the interstitial space, and as the pressure falls along the length of the capillary, the tendency shifts toward reabsorbing fluid back into the capillary (or draining it via lymphatics) near the venous end. In short: higher at the arterial end, it drops along the capillary, promoting filtration early and reabsorption later.