AEMCA Practice Exam

Which of the following describes the first stage of hemostasis?

1. Formation of a platelet plug

2. Vascular spasms causing vasoconstriction

3. Coagulation with clotting factors

4. Activation of A antibodies

The correct answer is: Vascular spasms causing vasoconstriction

The first stage of hemostasis is characterized by vascular spasms that lead to vasoconstriction. This response occurs immediately after a blood vessel is injured. The primary purpose of this vasoconstriction is to reduce blood flow to the affected area and minimize blood loss. It is an essential initial reaction that helps to stabilize the situation and sets the stage for the subsequent phases of hemostasis. During this phase, damaged blood vessels release substances that lead to the contraction of the smooth muscle in the vessel walls. This involves the release of factors such as endothelin, which promote vasoconstriction, and also the response of surrounding tissues to injury. The reduction in blood flow aids in the formation of a more stable hemostatic plug as other hemostatic processes occur, such as the recruitment and aggregation of platelets in later stages. In the context of hemostasis, understanding that vascular spasms are the immediate response to vessel injury is crucial. This stage lays the groundwork for the eventual formation of the platelet plug and blood clot, which are crucial for stopping bleeding.