Final answer:
The capillary tube allows the high and low sides of the system to equalize on the reabsorption cycle, during which fluid re-enters the capillary due to differences in BCOP and CHP.
Step-by-step explanation:
During the reabsorption cycle, the capillary tube enables the system's high and low sides to equalize. Net filtration and net reabsorption of fluid occur during capillary exchange, a vital physiological process in the circulatory system. Because capillary hydrostatic pressure (CHP) is higher than blood colloidal osmotic pressure (BCOP) close to the artery end of the capillary, net filtration takes place there. Since CHP equals BCOP, there is no net fluid movement at the capillary's midpoint. Net reabsorption occurs near the venous end when BCOP is greater than CHP.
This process ensures that fluids and dissolved substances are efficiently exchanged between blood and tissues. Following exchange in the systemic capillaries, oxygen and nutrients move out of the capillaries and carbon dioxide and wastes move in, with blood eventually returning to the heart to complete the cycle.
In terms of physical systems like a manometer exposed to the atmosphere, the fluid levels reach equilibrium regardless of tube diameters due to the principle that fluids in open systems will equalize at the same pressure level.