Haemostasis Flashcards
What is haemostasis?
Stopping bleeding whilst maintaining blood flow elsewhere
What happens to vessels when they are injured?
Contraction
Activation of plaelets
When does primary and secondary haemostasis occur?
Primary - small injury (platelets and vWF)
Secondary - large defect (requires fibrin stabilisation)
What are the 5 platelet functions?
Adhesion of platelet to endothelium Aggregation Secretion of thromboxane, serotonin Procoagulant surface Clot retraction
What are the 3 components of haemostasis? (all happen simultaneously)
Primary haemostasis
Seconday haemostasis
Tertiary haemostasis
What is primary haemostasis?
Formation of primary platelet plug
What is secondary haemotasis?
Formation of definitive clot (AKA coagulation)
What is tertiary haemostasis?
Fibrinolysis
What is von Willebrand factor?
Glycoprotein in haemostasis - binds to platelets
Describe primary haemostasis
Vascular endothelial damage exposes collagen and von Willebrand bings to platelets
P-selectin induces rolling of platelets and WBCs
Platelets activated
Secondary haemostasis involves converting what? What enzyme mediates this?
Fibrinogen to fibrin
Thrombin
What is the purpose of fibrin in the secondary haemostats stage, coagulation?
Fibrin cross links to make plug more stable
What happens during the tertiary phase of haemostasis? What mediates this?
Lysis of platelet-fibrin network
Plasmin
What causes inactivation of thrombin in fibrinolysis (tertiary haemostasis)? Where is this produced?
Antithrombin III
What is the coagulation cascade?
Series of enzyme activations
Causes production of thrombin which converts fibrinogen to fibrin
