Question

A person met with a small accident and bleeds, but very soon stops bleeding. Explain the physiological process responsible for this.

Hint:

The coagulation cascade involves intrinsic and extrinsic pathways, both converging to activate thrombin.

Answer 1

Step 1: Hemostasis is the physiological process that stops bleeding. It involves three stages: 1. Vascular spasm: Blood vessels constrict to reduce blood flow at the injury site. 2. Platelet plug formation: Platelets adhere to the damaged endothelium, releasing chemicals (e.g., ADP, thromboxane) to attract more platelets, forming a temporary plug. 3. Coagulation: A cascade of clotting factors (e.g., thrombin converts fibrinogen to fibrin) forms a stable fibrin clot, sealing the wound. Step 2: For a small injury, the process is rapid, with the clot reinforced by fibrin within minutes, stopping bleeding. The clot later retracts, and tissue repair begins.