Hematology is the branch of medicine that studies and treats diseases of the blood, including diseases related to blood platelets, according to the American Society of Hematology. Platelets aid in blood clotting, so many platelet disorders involve too much or too little clotting, contributing to cardiovascular disease or bleeding disorders.
Blood platelets form in the bone marrow along with red and white blood cells, but blood platelets are not themselves cells. Originally thought to be dust in the blood, platelets are actually cell fragments. After an injury, they build a scaffolding around damaged blood vessels, which allows clotting to occur.