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What is the function of platelets?

The principal function of platelets is to prevent bleeding.   Platelets are not only the smallest blood cell, they are the lightest.  Therefore they are pushed out from the center of flowing blood to the wall of the blood vessel.  There they roll along the surface of the vessel wall, which is lined by cells called endothelium.  The endothelium is a very special surface, like Teflon, that prevents anything from sticking to it.  However when there is an injury or cut, and the endothelial layer is broken, the tough fibers that surround a blood vessel are exposed to the liquid flowing blood.  It is the platelets that react first to injury.  The tough fibers surrounding the vessel wall, like an envelop, attract platelets like a magnet, stimulate the shape change and platelets then clump onto these fibers, providing the initial seal to prevent bleeding, the leak of red blood cells and plasma through the vessel injury.


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