What are the components needed for blood clotting, formed in the bone marrow?

The components necessary for blood clotting that are formed in the bone marrow are platelets. Platelets, also known as thrombocytes, are small cell fragments that play a crucial role in the coagulation process. When a blood vessel is injured, platelets quickly adhere to the site of the injury and to each other, forming a temporary "clot" that helps to control bleeding. This process is vital for wound healing and maintaining hemostasis.

In contrast, leukocytes, or white blood cells, are primarily involved in the immune response and do not play a direct role in blood clotting. Hemoglobin is a protein found in red blood cells (erythrocytes) that is responsible for oxygen transport, but it is not involved in the clotting process. Erythrocytes themselves are responsible for carrying oxygen from the lungs to the body’s tissues and do not contribute to the formation of blood clots. Thus, the correct answer is due to platelets' specific function in the coagulation pathway, distinguishing them from the other blood components.