Blood Clotting Flashcards
Coagulation
solid blood clot formation to prevent blood loss after damage to the lining of blood vessels
Hemostasis
blood is maintained in fluid clot-free state, but ready to clot in response to injury
Clotting process
- Platelet (Thrombocyte) Aggregation: platelets adhere/aggregate to injured endothelium
- Activation of soluble factors: inactive fibrinogen converted to fibrin, fibrin forms a meshwork = solid clot
Blood components
45% cells (RBC+WBC+platelets), 55% plasma
Serum
liquid left over after clotting
Platelet formation
stem cell (in bone marrow) - megakaryoblast - megakaryocyte - breakup of cell as fingers protrude from bone marrow into bloodstream - platelets
Injury to endothelium
- exposes collagen 2. von Willebrand Factor produced (bridge from platelet to endothelium) These events enable platelet adhesion via platelet receptors
After adhesion, platelets…
- secrete contents of granules (e.g. ADP, calcium, histamine, serotonin) 2. produce Thromboxane A2 These events amplify the platelet activation response and enable platelet aggregation = primary hemostatic plug
Thromboxane A2
stimulates activation of new platelets as well as increases platelet aggregation
Prostacycline
secreted by normal endothelium, inhibits platelet aggregation
Thrombopoietin
regulates the production of platelets - platelets and megakaryocytes both have receptors
Thrombin
converts fibrinogen (soluble) to fibrin (insoluble)
Secondary hemostatic plug
fibrin deposition
Clotting Factor activation
activates prothrombin to thrombin, via intrinsic or extrinsic pathways (often both)
Intrinsic Pathway
initiated by factors within the blood (e.g. activated platelets) or negatively charged surfaces (e.g. glass surface).