The first event in blood clotting is

Options

A. Release of coagulation promoting substances from platelets
B. conversion of prothombin to thrombin
C. Conversion of fibrogen to flavin
D. Formation of enzymes complex thombokinase

Answer

**Step-by-Step Text Solution:**

1. **Understanding Blood Clotting Process**: Blood clotting, also known as coagulation, is a complex process that prevents excessive bleeding when there is an injury to a blood vessel.

2. **Initial Trigger**: The first event in blood clotting occurs when a blood vessel is damaged, leading to the exposure of collagen fibers and the release of certain substances.

3. **Release of Coagulation Promoting Substances**: The first significant step in the clotting process is the release of coagulation promoting substances from platelets. Platelets are small cell fragments in the blood that play a crucial role in hemostasis (the process of stopping bleeding).

4. **Activation of Prothrombin**: Following the release of these substances, prothrombin (a plasma protein) is activated to thrombin. This activation is essential for the subsequent steps in the clotting cascade.

5. **Conversion of Fibrinogen to Fibrin**: Thrombin then converts fibrinogen (another plasma protein) into fibrin, which is the protein that forms the mesh-like structure of a blood clot.

6. **Formation of the Clot**: The fibrin strands weave through the platelets and other cells at the site of injury, forming a stable blood clot that effectively seals the wound.

7. **Conclusion**: Therefore, the first event in blood clotting is the release of coagulation promoting substances from platelets.

**Final Answer**: The first event in blood clotting is the release of coagulation promoting substances from platelets.

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