Final answer:
Net hydrostatic pressure in capillary exchange is determined by subtracting the blood colloid osmotic pressure from the capillary hydrostatic pressure, which involves the balance of forces pushing fluid out of the capillaries and the opposing osmotic pressures that pull fluid back in.
Step-by-step explanation:
In normal capillary exchange, the net hydrostatic pressure is based on capillary hydrostatic pressure (CHP) and interstitial fluid hydrostatic pressure (IFHP).
CHP is the force exerted by blood against the walls of capillaries, primarily resulting from the pumping action of the heart. At the arteriolar end of the capillary, this pressure tends to be higher, promoting filtration of fluids and nutrients out of the blood vessels and into the surrounding tissues. Conversely, IFHP is the opposing pressure within the interstitial fluid, which rises as fluid accumulates. It is worth noting that lymphatic vessels continuously drain this excess fluid from the tissues, generally keeping the IFHP lower than CHP.
Osmotic pressure, especially blood colloid osmotic pressure (BCOP), is determined by the osmotic concentration gradients between the blood and the interstitial fluid, and is influenced by plasma proteins like albumin. BCOP opposes hydrostatic pressure and promotes the reabsorption of fluids back into the capillaries. The dynamic between these pressures is crucial for maintaining fluid balance within the body.
To calculate the net filtration pressure (NFP), one must consider both hydrostatic and osmotic pressures. The formula for NFP is calculated by subtracting the blood colloid osmotic pressure from the capillary hydrostatic pressure, which represents the pushing force exerted by the blood minus the pulling force exerted by the blood proteins.