Fluids in organisms often move because of an osmotic gradient. Some materials move through cell membranes because of active transport which takes energy. Capillaries tend to leak out fluid, probably because of the blood pressure of the system and they don't have many cell layers. . The proteins in the blood actually act to create an osmotic pressure to bring back into the veins/venules this leaked fluid. That's why starving children... who are starving due to inadequate protein intake often look bloated.... but that edema is because of the leakage of water from the capillaries which remains in the tissues.
membranes and osmosis pressures
Capillary exchange play an important role in homeostasis, it involve the processes of that moves materials across typical capillary wall like diffusion, filtration and reabsorption.
fluid entering the capillary
Osmotic pressure is what draws fluid back into the capillary from the tissues.
capillary network
Arteriole
Blood colloid osmotic pressure
Capillary endothelium
is the force responsible for moving fluid across capillary walls. It is the difference between net hydrostatic pressure and net osmotic pressure. NFP= Net hydrostatic pressure - net osmotic pressure
Capillary hydrostatic pressure and interstitial fluid osmotic pressure
Blood hydrostatic pressure.
The first capillary bed in the series is the glomerular capillary, where filtration occurs. The efferent arteriole on the distal end of the glomerular capillary. Objects it to the next capillary bed in the series: the peritubular capillary. This is where secretion and reabsorbtion take place. This type of system is an example of an arterial portal system.