Exchange of materials between blood and tissue

• As blood flows through the capillaries it slows; due to thin, permeable walls and the high blood/hydrostatic pressure forcing plasma out into spaces between body cells (tissue fluid), when plasma leaves the blood, dissolved nutrients and oxygen go to; they diffuse into the body cells from the tissue fluid
• Most tissue fluid returns to capillaries wih waste materials (e.g. CO_2), which has diffused in from the body cells; some passes into the lymph vessels to become lymph (Fluid in the lymphatic system and consists of 95% water plus protein, glucose, salts, lymphocytes and macrophages, similar to plasma, but fewer proteins)