blood coagulation

Definition

Target type: biologicalprocess

The sequential process in which the multiple coagulation factors of the blood interact, ultimately resulting in the formation of an insoluble fibrin clot; it may be divided into three stages: stage 1, the formation of intrinsic and extrinsic prothrombin converting principle; stage 2, the formation of thrombin; stage 3, the formation of stable fibrin polymers. [PMID:30700128]

Blood coagulation, also known as clotting, is a complex process that stops bleeding by forming a blood clot. It is essential for maintaining hemostasis, the balance between blood flow and clotting. Here's a detailed description of the process:

1. **Vascular Spasm:** When a blood vessel is injured, the smooth muscle in its walls constricts, reducing blood flow to the area. This is a temporary measure that helps reduce blood loss.

2. **Platelet Plug Formation:** Platelets, small cell fragments found in blood, adhere to the exposed collagen in the injured vessel wall. They release chemicals like adenosine diphosphate (ADP) and thromboxane A2, which attract more platelets to the site. These platelets aggregate and form a temporary plug, further reducing blood loss.

3. **Coagulation Cascade:** This is the main event in blood clotting. It involves a series of enzymatic reactions that ultimately convert fibrinogen, a soluble protein in plasma, into fibrin, an insoluble protein that forms the meshwork of the clot. The cascade is divided into three main pathways:
- **Intrinsic Pathway:** Activated by contact with negatively charged surfaces, such as exposed collagen or glass. This pathway involves factors XII, XI, IX, VIII, and X.
- **Extrinsic Pathway:** Triggered by the release of tissue factor (TF) from damaged cells. TF activates factor VII, which then activates factor X.
- **Common Pathway:** Both the intrinsic and extrinsic pathways converge at factor X activation. Factor X, along with factor V, prothrombin, and calcium, converts prothrombin into thrombin. Thrombin then converts fibrinogen into fibrin.

4. **Fibrin Mesh Formation:** Fibrin molecules polymerize, forming long fibers that entrap red blood cells, platelets, and other blood components, creating a stable clot.

5. **Clot Retraction:** Once the clot is formed, it begins to contract, squeezing out serum and drawing the edges of the wound closer together. This helps to stabilize the clot and promote healing.

6. **Fibrinolysis:** After the wound heals, the clot is dissolved through a process called fibrinolysis. Plasminogen, an inactive enzyme in plasma, is converted to plasmin by tissue plasminogen activator (tPA) and urokinase. Plasmin breaks down fibrin, dissolving the clot and restoring blood flow.'
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Proteins (34)

Compounds (1,252)