Final answer:
The statement that fluids leave the capillaries on the arterial side and reenter on the venous side is correct. Net filtration facilitated by the hydrostatic and osmotic pressures occurs near the arterial end, while reabsorption happens near the venous end. Additionally, erythrocytes take up oxygen in the capillaries, and carbon dioxide is transferred from tissues back into the circulating blood.
Step-by-step explanation:
Among the provided statements regarding a capillary bed, the correct statement is that fluids will leave the capillaries on the arterial side and reenter on the venous side. This process is facilitated by the difference in pressures along the capillary bed: the capillary hydrostatic pressure (CHP), which is the pressure exerted by fluid in an enclosed space, and the blood colloidal osmotic pressure (BCOP), which is generated by plasma proteins that cannot pass through the capillary walls. At the arterial end of the capillaries, the CHP is higher than BCOP, causing net filtration of fluid out of the capillaries. Near the midpoint, there is no net movement of fluid since CHP equals BCOP. Then, near the venous end, BCOP is greater than CHP, leading to net reabsorption of fluid back into the capillaries.
In relation to oxygen exchange, erythrocytes within the capillaries take up oxygen. The partial pressure of oxygen (Po_2) is higher in the lungs compared to the capillaries, creating a gradient that allows oxygen to diffuse from the alveoli into the erythrocytes where it binds to hemoglobin. As for carbon dioxide, a pressure gradient facilitates its movement from the tissues, which have a higher partial pressure of CO_2 (Pco_2), into the capillaries where it's taken up by the blood to be transported back to the lungs.
Oxygen saturation does not affect hydrostatic pressure, and the pH typically is lower on the venous side because of the higher concentration of carbon dioxide, which forms carbonic acid in the blood. Lastly, osmotic pressure does not remain constant; it is determined primarily by the concentration of plasma proteins and not by carbon dioxide concentration.