Progressive Care Nursing Certification (PCCN) Practice Exam

Why is calcium required for clot formation?

1. Calcium reacts with factor Xa to begin the common pathway of clot formation

2. Calcium is necessary for contraction of vascular smooth muscle

3. Calcium is necessary for bone conservation

4. Calcium is a by-product of glucose metabolism

The correct answer is: Calcium reacts with factor Xa to begin the common pathway of clot formation

Calcium plays a pivotal role in the clotting process by serving as a cofactor for several steps in the coagulation cascade. Specifically, it is essential for the conversion of prothrombin to thrombin, as well as for the activation of clotting factors that ultimately lead to the formation of fibrin, the protein that forms the mesh of a blood clot. When calcium ions are present, they facilitate the interaction of certain coagulation factors, such as factor Xa, within the common pathway of the clotting cascade. This activation is crucial for maintaining hemostasis and preventing excessive bleeding. The other options, while related to calcium’s various functions in the body, do not explain its essential role in the context of clot formation. Calcium's involvement in muscle contraction pertains to vascular smooth muscle primarily related to vascular tone rather than directly to the clotting process. The reference to bone conservation does not pertain to the coagulation pathway, and glucose metabolism's by-products do not include calcium, highlighting an unrelated function.