Coagulation Exam 4 Flashcards
What is the definition of coagulation?
The process that prevents and stops bleeding, involving the transformation of blood from a liquid to a gel.
What is hemostasis?
Normal hemostasis is a balance between clot generation, thrombus formation, and regulatory mechanisms that inhibit uncontrolled thrombogenesis.
What are the goals of hemostasis?
- Limit blood loss from vascular injury
- Maintain intravascular blood flow
- Promote revascularization after thrombosis
What are the two stages of hemostasis?
- Primary Hemostasis
- Secondary Hemostasis
What occurs during primary hemostasis?
Immediate platelet deposition at the endovascular injury site leads to initial platelet plug formation.
What occurs during secondary hemostasis?
Clotting factors are activated, leading to a stabilized clot formed and secured with crosslinked fibrin.
What role do vascular endothelial cells play in hemostasis?
They have antiplatelet, anticoagulant, and fibrolytic effects to inhibit clot formation.
What are the anti-clotting mechanisms of endothelial cells?
- Negatively charged to repel platelets
- Produce platelet inhibitors such as prostacyclin and nitric oxide
- Excrete adenosine diphosphatase, degrading ADP
- Increase protein C, an anticoagulant
- Produce Tissue Factor Pathway Inhibitor (TFPI)
- Synthesize tissue plasminogen activator (t-PA)
What is the lifespan of platelets?
8-12 days.
What describes the structure of inactive platelets?
They circulate as disc-shaped anuclear cells.
What are the three phases of platelet alteration upon endothelial damage?
- Adhesion
- Activation
- Aggregation
What initiates platelet adhesion?
Exposure to extracellular matrix (ECM) proteins.
What triggers platelet activation?
Interaction with collagen and tissue factor (TF), causing the release of granular contents.
What do alpha granules in platelets contain?
- Fibrinogen
- Factors V & VIII
- von Willebrand factor (vWF)
- Platelet-derived growth factor
- More
What do dense bodies in platelets contain?
- ADP
- ATP
- Calcium
- Serotonin
- Histamine
- Epinephrine
What is the Extrinsic Pathway in hemostasis?
The initiation phase of plasma-mediated hemostasis that begins with endothelial injury, exposing TF to the plasma.
What is the role of the TF/VIIa complex?
It binds to and activates factor X, converting it to Xa, and also activates factor IX in the intrinsic pathway.
What is the intrinsic pathway’s current understanding in hemostasis?
It plays a minor role in initiation and is more of an amplification system for thrombin generation initiated by the extrinsic pathway.
What activates factor XII in the intrinsic pathway?
Contact with a negatively charged surface.
What is the final common pathway in hemostasis?
It begins with factor Xa binding with Va to form the prothrombinase complex, converting prothrombin into thrombin.
What stabilizes the clot during hemostasis?
Fibrin molecules crosslink to form a mesh that stabilizes the clot.
What are the four major coagulation counter-mechanisms?
- Fibrinolysis
- Tissue factor pathway inhibitor (TFPI)
- Protein C system
- Serine Protease Inhibitors (SERPINs)
What is the role of fibrinolysis?
Endovascular tPA and urokinase convert plasminogen to plasmin, which breaks down clots.
What does the Protein C system inhibit?
Factors II, Va, and VIIIa.