The blood pressure in the veins is insufficient to return blood to the heart, particularly form the outermost extremities. Therefore, the flow of blood back to the heart is assisted by the massaging action on the veins of the skeletal muscles as they contract by the assistance of venous valves. The action of the platelets and the coag factors is known as homeostasis. The body's line of defense lies with the blood vessels to contract at the injury site. This will cause a decrease in the flow of blood along with the platelets taking action to form the clot which will assist in the bleeding to stop.
Platelets are small cells that are found in the peripheral blood.
Although platelets play a major role in coagulation, they also support uninjured endothelial tissue as they form a plug by adhering to the injured tissue. In this process, the platelets release their clotting factors called aggregating agents . Besides attracting more platelets to the injury site, these agents also call for further contraction of the blood vessel and are involved in the activation of the coag factors. A lack of platelet function or a decrease in there numbers, directly effect the hemostatic scheme. This is very vital in the formation of the plug that the platelets form in a vascular injury and in supplying phospholipids.