Canadian Society for Medical Laboratory Science (CSMLS) Practice Exam

Which component of blood is responsible for clotting?

1. Erythrocytes

2. Leukocytes

3. Platelets

4. Plasma

The correct answer is: Platelets

The component of blood responsible for clotting is platelets. Platelets, also known as thrombocytes, are small, disc-shaped cell fragments that play a crucial role in hemostasis, which is the process of stopping bleeding. When a blood vessel is injured, platelets quickly adhere to the site of injury and to each other, forming a temporary plug. This aggregation helps to minimize blood loss and sets the stage for further clotting processes, which involve coagulation factors present in the plasma. Erythrocytes, or red blood cells, primarily function to transport oxygen and carbon dioxide between the lungs and tissues. They do not play a direct role in the clotting process. Leukocytes, or white blood cells, are primarily involved in the immune response and also do not contribute to clot formation. Plasma is the liquid component of blood that carries cells and proteins; it contains clotting factors, but it is the platelets that are directly involved in the initial stages of clot formation.