Final answer:
Typical capillary pressures, or capillary hydrostatic pressure (CHP), start at around 35 mm Hg and decrease to approximately 18 mm Hg as blood moves through the capillary. Blood colloid osmotic pressure (BCOP), generated by plasma proteins, remains constant at about 25 mm Hg, while the pressure from proteins alone is around 30 mm Hg. These pressures balance to facilitate the exchange of substances between the bloodstream and tissues.
Step-by-step explanation:
The typical capillary pressures, also known as capillary hydrostatic pressure (CHP), vary within the cardiovascular system. When blood enters a capillary bed from an arteriole, the CHP starts high at about 35 mm Hg and then decreases as blood moves through the capillary, reaching approximately 18 mm Hg by the venous end. In contrast, the blood colloid osmotic pressure (BCOP), generated by plasma proteins suspended in the blood, remains fairly constant at around 25 mm Hg throughout the capillary. This constant BCOP acts against the hydrostatic pressure to maintain the net filtration pressure (NFP), which is crucial for the exchange of water and other substances between blood vessels and tissues.
The protein-generated pressure, which is the osmotic pressure exerted by proteins in the blood, remains at about 30 mm Hg due to the presence of proteins like albumins that cannot pass through the capillary walls.
Regulation of water passage:
If capillary pressure increases, more water flows into the tissues.
A decrease in blood pressure facilitates the movement of water from the tissues back into the blood.
A reduction in plasma proteins leads to an increased flow of water into the tissues.
Overhydration can dilute blood plasma, which may lower the osmotic pressure exerted by plasma proteins and, in turn, affect capillary pressure.