Final answer:
Platelets are small cell fragments involved in blood clotting. They are formed from megakaryocytes and help form clots to prevent blood loss and bacterial entry.
Step-by-step explanation:
Platelets are very small cell fragments involved in blood clotting. They are formed from large cells called megakaryocytes in the bone marrow. When a blood vessel gets cut, platelets stick to the injured area and release clotting factors, which cause proteins to form over the wound and form a clot. Platelets are important in preventing blood loss and stopping bacteria from entering the body.