Canadian Society for Medical Laboratory Science (CSMLS) Practice Exam

Which blood component is primarily responsible for clotting?

1. Erythrocytes

2. Leukocytes

3. Platelets

4. Plasma

The correct answer is: Platelets

Platelets, also known as thrombocytes, are the blood components primarily responsible for the process of clotting, or hemostasis. When a blood vessel is injured, platelets quickly adhere to the exposed site, where they become activated and aggregate to form a temporary "platelet plug." This action is pivotal in stopping the bleeding. Additionally, platelets release various substances that facilitate the recruitment of other platelets and initiate a cascade of reactions that lead to the formation of a stable blood clot. In contrast, erythrocytes (red blood cells) are primarily responsible for transporting oxygen and carbon dioxide throughout the body, while leukocytes (white blood cells) are integral to the immune response and defense against infections. Plasma is the liquid component of blood that carries cells, nutrients, hormones, and waste products, but it does not play a direct role in the process of clotting itself. Thus, the function of platelets in clotting is both critical and specific, distinguishing them as the key players in this aspect of hemostasis.