Question

How do hydrostatic and osmotic pressures determine fluid movement across the walls of capillaries?

Answer 1

Capillaries are the smallest blood vessels that carry the blood to every tissue and cell in the body. In capillaries the gases and nutrients diffuse into tissues and also enters at the other end, based on hydrostatics pressure and osmotic pressure. The hydrostatic pressure in the pressure created by the fluids in the blood vessel, which is exerted on the walls of the capillaries. The osmotic pressure acts in opposite direction from outside towards inside capillaries. Thus these two forces counterbalance each other and maintain the flow of fluids across the walls. If the solute concentration is more in the capillaries then the osmotic pressure will be less and hydrostatic pressure is more, allowing fluid movement out of the capillaries into interstitial tissue. If solute inside the capillaries is less, then the net movement occurs from outside to inside of the capillaries.