Tissue Fluid

• capillaries have thin walls to decrease diffusion pathway
• capillary have fenestrations which allow large molecules through
• the narrow lumen in capillary shorten diffusion pathway, increases s.a. , and allows red blood cells to pass singly ; reducing rate of blood flow
• when talking about tissue fluids always mention osmosis and hydrostatic pressure
• Because of the high hydrostatic pressure in the capillary, the products inside are forced out along the concentration gradient into the tissues. This creates a lower water potential in the capillary, and a higher HP in the tissues. When the blood arrives at the arteriole end, tissue fluid is already surrounding the capillary bed.