Platelets are the smallest of the human blood cells, measuring about one-tenth the diameter of a white blood cell. They usually circulate freely, maintained in a mobile but inactive state by molecules ...

PHILADELPHIA — Blood platelets shore up open wounds and help cuts heal, but they can also cause heart attacks and strokes when a congealed ball of platelets known as a thrombus breaks free from a site ...

When the body experiences an injury to a blood vessel, muscular response to the injury causes the vessel to constrict, decreasing blood flow to the area. The blood is exposed to collagen in the ...