Body Parts: Platelets play critical role in blood clotting. Blood platelets are tiny cellfragments that play a critical role in blood clotting. They are produced in the bone marrow by large cells called megakarocytes. These cells break apart to form platelets, which then circulate in the blood.
The normal platelet count is 150,000-350,000 per microliter of blood, but since platelets are so small, they make up just a tiny fraction of the blood volume. The principal function of platelets is to prevent bleeding. Red blood cells are the most numerous blood cell, about 5,000,000 per microliter.