For bulk flow across capillary walls,________.
A) hydrostatic pressure of the interstitial space returns fluid to the capillary
B) fluid runs into lymphatic capillaries that empty into the interstitial space
C) hydrostatic pressure of blood forces nearly protein-free plasma out of the blood into the interstitial space
D) osmotic pressure of plasma proteins pulls fluid from the capillary into the interstitial space

Question

Quizplus · Accepted Answer

Bulk flow across capillary walls is primarily influenced by two forces: hydrostatic pressure and osmotic pressure. Hydrostatic pressure is generated by the blood in the capillaries, and it forces fluid out of the capillary and into the interstitial space. This is balanced by osmotic pressure, which is determined by the presence of plasma proteins in the blood. The pressure exerted by these proteins tends to draw fluid back into the capillary. In the case of bulk flow, the hydrostatic pressure is strong enough to overcome the osmotic pressure, and fluid is pushed out of the capillary and into the interstitial space. This fluid is nearly protein-free because most of the proteins are too large to pass through the capillary walls. Eventually, the fluid is returned to the bloodstream via the lymphatic system.

For Bulk Flow Across Capillary Walls,________