Haemostasis
When a blood vessel is damaged, loss of blood is stopped and healing occurs in a series of overlapping processes, in which platelets play a vital part, The more badly damaged the vessel wall is, the faster coagulation begins, sometimes as quickly as 15 seconds after injury.
1. Vasoconstriction- platelets come into contact with the damaged blood vessel, there surface becomes sticky and they adhere to the damaged wall, then they release serotonin(5-hydroxytrptamine), which constricts the vessel, reducing blood flow through it. other chemicals that cause vasoconstriction, e.g. thromboxanes, are released by the damaged vessel itself.
2. Platelet plug formation- The adherent platelets clump to each other and release, other substances, including adinosine diphosphasate(ADP), which attract more platelets to the site. Passing platelets stick to those already at the damaged vessel and they too release their chemicals. This is a positive feedback system by which many platelets rapidly arrive at the site of vascular damage and quickly form a temporary seal-the platelet plug. Platelet plug formation is usually complete by 6 minutes after injury.
3. Fibrinolysis- After the clot has formed the process of removing it and healing the damaged blood vessel begins.The breakdown of the clot or fibrinolysis, is the first stage. An inactive substance called plasminogen is present in the clot and is converted to the enzyme plasmin by activators released from the damaged endothelial cells.cells. Plasmin initiates the breakdown of fibrin to soluble products that are treated as waste material and removed by phagocytosis. As.As the clot removed the healing process restores the ingratiate blood vessel.
When a blood vessel is damaged, loss of blood is stopped and healing occurs in a series of overlapping processes, in which platelets play a vital part, The more badly damaged the vessel wall is, the faster coagulation begins, sometimes as quickly as 15 seconds after injury.
1. Vasoconstriction- platelets come into contact with the damaged blood vessel, there surface becomes sticky and they adhere to the damaged wall, then they release serotonin(5-hydroxytrptamine), which constricts the vessel, reducing blood flow through it. other chemicals that cause vasoconstriction, e.g. thromboxanes, are released by the damaged vessel itself.
2. Platelet plug formation- The adherent platelets clump to each other and release, other substances, including adinosine diphosphasate(ADP), which attract more platelets to the site. Passing platelets stick to those already at the damaged vessel and they too release their chemicals. This is a positive feedback system by which many platelets rapidly arrive at the site of vascular damage and quickly form a temporary seal-the platelet plug. Platelet plug formation is usually complete by 6 minutes after injury.3. Fibrinolysis- After the clot has formed the process of removing it and healing the damaged blood vessel begins.The breakdown of the clot or fibrinolysis, is the first stage. An inactive substance called plasminogen is present in the clot and is converted to the enzyme plasmin by activators released from the damaged endothelial cells.cells. Plasmin initiates the breakdown of fibrin to soluble products that are treated as waste material and removed by phagocytosis. As.As the clot removed the healing process restores the ingratiate blood vessel.
