Where and from which cells do platelets originate? What Is their life span? How do they act when blood vessels get injured?

Where and from which cells do platelets originate? What Is their life

1.	Where and from which cells do platelets originate? What Is their life span? How do they act when blood vessels get injured?
Answer» Platelets originate from the megakaryocytes in the bone marrow. They live for about seven days. They release thromboplastins, which help convert prothrombin of the plasma into thrombin and thus help in clotting of blood.