Local conditions, such as need for more oxygen and nutrients in active skeletal muscle, cause changes in the rate of flow near those tissues. From Capillary Beds Back to the Heart Capillary Function Capillaries are diffusion zones for exchanges between blood and interstitial fluid. Venous Pressure Capillaries merge into venules, then into veins. The movement of skeletal muscles squeezes the veins and pushes the blood along against the forces of gravity. Hemostasis Hemostasis is the process of repairing the damage when a blood vessel ruptures.
Platelets clump to plug the rupture.
The human body also has antibodies that recognize markers on foreign cells. In a blood transfusion, or even a pregnancy, it is important that there is no possibility of an interaction between antibodies and foreign markers. ABO Blood Typing ABO blood typing is based on surface markers on red blood cells. In erythroblastosis fetalis, too many cells may be destroyed and the fetus dies. The lymphatic system returns excess tissue fluid to the bloodstream via transport tubes.