Haemostasis Flashcards
(17 cards)
What is haemostasis?
The process to stop bleeding, including vascular spasm, platelet plug formation, and blood coagulation.
What causes vascular spasm in haemostasis?
Direct injury to vascular smooth muscle, chemicals from endothelial cells and platelets, and pain receptor reflexes.
What happens during platelet plug formation?
Platelets adhere to exposed collagen via von Willebrand factor, activate, change conformation, and release ADP and thromboxane A2 (TXA2).
What are the functions of the platelet plug?
Seals the vessel break, compacts the plug via actin-myosin, releases vasoconstrictors, and mediators for coagulation.
What is blood coagulation?
The transformation of blood from a liquid to a solid gel, with fibrinogen converting to fibrin.
What role does thrombin play in blood coagulation?
Converts fibrinogen into fibrin, activates factor XIII, enhances platelet aggregation, and induces its own formation.
What are the intrinsic and extrinsic pathways in the clotting cascade?
Intrinsic pathway involves factor XII (Hageman factor), while the extrinsic pathway involves tissue thromboplastin (factor III). Both converge at factor X activation.
What happens during clot retraction?
Occurs 30-60 minutes post-clotting, involves serum release and vessel repair with PDGF and VEGF.
What is fibrinolysis?
The process of clot dissolution via plasminogen converting to plasmin over 2 days.
How is inappropriate clot formation prevented?
Through antithrombin III, protein C, heparin, and tissue plasminogen activator (tPA).
What are the causes of bleeding disorders?
Platelet deficiency (thrombocytopenia), impaired liver function, vitamin K deficiency, hepatitis, cirrhosis, and genetic conditions like haemophilia.
What are the types of haemophilia?
Haemophilia A (factor VIII deficiency) and Haemophilia B (factor IX deficiency).
What is a thrombus?
An abnormal intravascular clot attached to a vessel wall.
What is an embolus?
A freely floating clot that can cause embolism.
What are possible causes of thromboembolic disorders?
Roughened vessel surfaces (atherosclerosis), imbalances in clotting systems, slow-moving blood, trauma, and septic shock.
What is thrombosis and its types?
Arterial occlusion (causing myocardial infarction, stroke, or ischaemia) and venous occlusion (causing deep vein thrombosis or pulmonary embolism).
What are the roles of fibrin and platelets in thrombosis?
Fibrin forms the clot structure, and platelets contribute to occlusion.
