Blood clotting, or coagulation, is a complex process involving a cascade of events and
multiple clotting factors. The process is essential for haemostasis, which is the cessation of
bleeding from a damaged blood vessel.
Here's a breakdown of the mechanism of clotting factors:
* **Initiation:**
* When a blood vessel is damaged, platelets come into contact with the damaged wall,
becoming sticky and adhering to it.
* The damaged tissue releases a complex of chemicals called **thromboplastin** or
tissue factor, which initiates the extrinsic pathway of coagulation.
* The intrinsic pathway is triggered when blood comes into contact with damaged blood
vessel lining (endothelium).
* **Vasoconstriction**: The damaged vessel constricts to reduce blood flow. Platelets also
release serotonin, which contributes to vasoconstriction.
* **Platelet plug formation:**
* Adherent platelets clump together and release substances like adenosine diphosphate
(ADP), which attract more platelets.
* This positive feedback system leads to the rapid formation of a temporary platelet plug.
* **Coagulation cascade**:
* Clotting factors activate each other in a specific sequence, eventually leading to the
formation of **prothrombin activator**.
* Prothrombin activator converts prothrombin to thrombin.
* Thrombin then converts inactive fibrinogen into insoluble fibrin threads.
* The fibrin threads form a meshwork that stabilises the platelet plug, trapping blood cells
and creating a stronger clot.
* **Fibrinolysis:**
* Once the clot has formed, the process of removing it and healing the blood vessel
begins.
* **Plasminogen**, an inactive substance in the clot, is converted to plasmin by
activators released from damaged endothelial cells.
* **Plasmin** breaks down fibrin into soluble products, which are then removed by
phagocytosis.
**Clotting Factors**:
* There are several clotting factors, each with a specific role in the coagulation cascade.
* These factors are designated by Roman numerals, and they activate each other in a
specific order.
* Some of the key clotting factors include:
* **Fibrinogen (Factor I):** Converted to fibrin.
* **Prothrombin (Factor II):** Converted to thrombin.
* **Tissue factor (Factor III):** Initiates the extrinsic pathway.
* **Calcium (Factor IV):** Essential for several steps in the cascade.
* **Vitamin K** is essential for the synthesis of factors II, VII, IX and X.
**Control of Coagulation**:
multiple clotting factors. The process is essential for haemostasis, which is the cessation of
bleeding from a damaged blood vessel.
Here's a breakdown of the mechanism of clotting factors:
* **Initiation:**
* When a blood vessel is damaged, platelets come into contact with the damaged wall,
becoming sticky and adhering to it.
* The damaged tissue releases a complex of chemicals called **thromboplastin** or
tissue factor, which initiates the extrinsic pathway of coagulation.
* The intrinsic pathway is triggered when blood comes into contact with damaged blood
vessel lining (endothelium).
* **Vasoconstriction**: The damaged vessel constricts to reduce blood flow. Platelets also
release serotonin, which contributes to vasoconstriction.
* **Platelet plug formation:**
* Adherent platelets clump together and release substances like adenosine diphosphate
(ADP), which attract more platelets.
* This positive feedback system leads to the rapid formation of a temporary platelet plug.
* **Coagulation cascade**:
* Clotting factors activate each other in a specific sequence, eventually leading to the
formation of **prothrombin activator**.
* Prothrombin activator converts prothrombin to thrombin.
* Thrombin then converts inactive fibrinogen into insoluble fibrin threads.
* The fibrin threads form a meshwork that stabilises the platelet plug, trapping blood cells
and creating a stronger clot.
* **Fibrinolysis:**
* Once the clot has formed, the process of removing it and healing the blood vessel
begins.
* **Plasminogen**, an inactive substance in the clot, is converted to plasmin by
activators released from damaged endothelial cells.
* **Plasmin** breaks down fibrin into soluble products, which are then removed by
phagocytosis.
**Clotting Factors**:
* There are several clotting factors, each with a specific role in the coagulation cascade.
* These factors are designated by Roman numerals, and they activate each other in a
specific order.
* Some of the key clotting factors include:
* **Fibrinogen (Factor I):** Converted to fibrin.
* **Prothrombin (Factor II):** Converted to thrombin.
* **Tissue factor (Factor III):** Initiates the extrinsic pathway.
* **Calcium (Factor IV):** Essential for several steps in the cascade.
* **Vitamin K** is essential for the synthesis of factors II, VII, IX and X.
**Control of Coagulation**:
