platelets are cell fragments derived from bone marrow cells called megakaryocytes. platelets circulate in blood but are much smaller than red or white blood cells. platelets are coated with substances that normally glide smoothly along the surface of blood vessels and other blood cells. however when platelets encounter a damaged blood vessel they collect together in a plug to stop the bleeding. a blood clot then forms sealing the platelet plug. aspirin and other medicines like clopidogrel (plavix) interfere with platelets’ ability to clump together. this helps protect against the sudden formation of blood clots inside blood vessels (the cause of heart attacks and strokes). antiplatelet drugs also increase the likelihood of abnormal or excessive bleeding.
what are platelets?