Question

multiple choice question
which statement best summarizes the general process of capillary fluid exchange?

○ tissue fluid enters the arterial end of a capillary bed. it is filtered to remove waste products, then leaves at the venous end.
○ fluid moves out of a capillary bed at the arterial end, exchanges materials with the tissue cells, then reenters the blood at the venous end.
○ fluid is osmotically pulled into the capillary bed along its entire length, causing a net increase in blood volume as it flows through the tissues.

Explanation:

To determine the correct summary of capillary fluid exchange, we analyze each option:

• First option: Tissue fluid doesn't enter the arterial end; blood plasma (not tissue fluid) is at the arterial end, so this is incorrect.
• Second option: At the arterial end of capillaries, hydrostatic pressure is higher, so fluid (plasma) moves out into tissues, exchanges materials with cells, and at the venous end, osmotic pressure pulls fluid (now with waste) back into the capillary. This matches the process.
• Third option: Fluid isn't pulled in along the entire length; at the arterial end, fluid moves out, and at the venous end, it moves in. Also, blood volume doesn't have a net increase as fluid lost at arterial end is mostly regained at venous end (with some going to lymph), so this is incorrect.

Answer:

B. Fluid moves out of a capillary bed at the arterial end, exchanges materials with the tissue cells, then reenters the blood at the venous end.