Haemostasis fundamentals ( 1 ) Flashcards
What is haemostasis?
Haemostasis is the balance of procoagulant and anticoagulant activity, involving vasculature, platelets, coagulation, fibrinolytic factors, and calcium ions.
What are the two main stages of haemostasis?
Primary Haemostasis – Platelet activation and aggregation.
Secondary Haemostasis – Coagulation factor cascade forming fibrin.
What is fibrinolysis?
The process that prevents excessive clot formation by breaking down fibrin.
What is the key function of platelets in haemostasis?
Platelets adhere to damaged endothelium, activate, release granules, and aggregate to form a temporary plug.
What role does thrombin play in coagulation?
Thrombin amplifies the clotting cascade, converts fibrinogen to fibrin, and stabilizes the clot.
What is the function of Factor XIIIa?
It crosslinks fibrin monomers to strengthen the clot.
What organ produces thrombopoietin (TPO) and what does it do?
The liver produces TPO, which regulates platelet production.
How do platelets adhere to endothelial damage?
They detect exposed collagen, bind von Willebrand Factor (VWF) via GPIb, and activate.
What key structural components do platelets have?
Glycoproteins (important for adhesion)
Microtubules & Actin (shape change)
Dense tubular system (calcium storage)
Dense bodies (ATP, ADP, serotonin)
Alpha granules (contain Factor V, VIII, VWF)
What are the vitamin K-dependent factors?
Procoagulation – II, VII, IX, X
Anticoagulation – Protein C, Protein S
What are the key factors in the intrinsic pathway?
Factors XII, XI, IX, and VIII.
What are the three steps of platelet activity?
Adhesion – Binding to VWF and collagen.
Activation – Release of ADP, calcium, and thromboxane A2.
Aggregation – GPIIb/IIIa binds fibrinogen, linking platelets.
What stabilizes the platelet plug?
Fibrin, which is produced via the coagulation cascade.
What happens in the common pathway?
Factor X → Factor Xa
Prothrombin (FII) → Thrombin (FIIa)
Fibrinogen (FGN) → Fibrin
What are the three pathways in the coagulation cascade?
Extrinsic pathway (Tissue factor pathway)
Intrinsic pathway (Contact activation pathway)
Common pathway (Final clot formation)
What are the key factors in the extrinsic pathway?
Tissue Factor (Factor III) and Factor VII.
How does warfarin work?
It inhibits the vitamin K cycle, reducing activation of coagulation factors.
What is thrombin’s role in back activation?
It activates Factors XI, V, and VIII, amplifying the clotting process.
