MTTC Integrated Science (Secondary) (094) Practice Test

Platelets are small, irregularly shaped cytoplasmic fragments derived from megakaryocytes that circulate in the blood and are essential for stopping bleeding. When a vessel is damaged, they adhere to the injury site, activate, and release granules that recruit more platelets and trigger the coagulation cascade, forming a platelet plug and helping to create a stable clot. They are not white blood cells (which fight infection), not red blood cells (which carry oxygen), and not plasma proteins that regulate blood pressure. This description best captures their role in clot formation and wound repair.