Which stable pressure drives filtration out of the capillary?

Hydrostatic pressure is the pressure exerted by the fluid within the capillaries, and it plays a crucial role in the process of filtration. This pressure is generated by the pumping action of the heart and is responsible for pushing blood and its components out of the capillaries and into the surrounding tissues. When the hydrostatic pressure within the capillaries is greater than the opposing forces, such as oncotic (or colloid osmotic) pressure, fluid moves out of the vessels.

This dynamic is essential in the context of fluid exchange between the blood and tissues, as it allows for nutrients, gases, and waste products to be effectively transferred. In healthy physiological conditions, hydrostatic pressure must be sufficiently maintained to ensure that adequate filtration and perfusion of tissues occur.

In contrast, oncotic pressure refers to the osmotic pull created by proteins in the blood, which draws water back into the capillaries. This balance between hydrostatic and oncotic pressures determines the direction and rate of fluid movement, but hydrostatic pressure is the primary driver that facilitates the outward filtration from the capillaries.