Final answer:
Platelets, which are fragments enclosed by a piece of the megakaryocytes' cell membrane, are essential for blood clotting, working with clotting factors to form a fibrin clot that prevents blood loss at a wound site.
Step-by-step explanation:
Cell fragments enclosed by a piece of the cell membrane of megakaryocytes and containing clotting factors are known as platelets or thrombocytes. Platelets are crucial for the blood clotting process, collecting at a wound site and working alongside clotting factors like fibrinogen to form a fibrin clot. This clot prevents blood loss and allows the wound to heal.
Megakaryocytes, large bone marrow cells derived from myeloid stem cells, release 2000-3000 platelets into the circulation during their lifespan. Release of these platelet precursors occurs through extensions that penetrate the walls of the bone marrow capillaries. Each platelet, measuring 2-4 μm in diameter and lacking a nucleus, can engage at the site of vascular injury to aid in the formation of a platelet plug or fibrin clot, crucial for hemostasis.