Description

Hemostasis is the body's natural process to stop bleeding and maintain blood flow within damaged blood vessels. It involves a complex interplay of blood vessels, platelets, and clotting factors to form a stable clot and prevent excessive blood loss. Stages of Hemostasis 1. Vascular Spasm (Vasoconstriction) Immediate response to injury: Damaged blood vessels constrict to reduce blood flow. Triggered by: Local pain signals. Endothelin (a potent vasoconstrictor). 2. Primary Hemostasis (Platelet Plug Formation) Platelets adhere to exposed collagen at the injury site. Activation: Platelets change shape, release granules (ADP, thromboxane A2). Aggregation: Platelets stick together, forming a temporary plug. 3. Secondary Hemostasis (Coagulation Cascade) A clotting factor cascade strengthens the platelet plug with fibrin. Extrinsic Pathway (Fast, triggered by tissue factor/TF). Intrinsic Pathway (Slower, activated by contact with collagen). Common Pathway: Both pathways converge to activate thrombin, which converts fibrinogen → fibrin mesh. 4. Clot Retraction & Fibrinolysis Clot retraction: Platelets contract, pulling edges of the wound together. Fibrinolysis: Plasmin breaks down the clot once healing is complete. Disorders of Hemostasis : 1. Bleeding Disorders (Failure of Hemostasis) Hemophilia (Factor VIII/IX deficiency). Von Willebrand Disease (vWF deficiency). Thrombocytopenia (Low platelets). 2. Thrombotic Disorders (Excessive Clotting) Deep Vein Thrombosis (DVT). Factor V Leiden mutation. Antiphospholipid syndrome.

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