hematology final - Sheet1 Flashcards
What is hemostasis?
Hemostasis is the process of arresting bleeding to prevent excessive blood loss after vascular injury.
What components are necessary for hemostasis?
Platelets, vasculature (endothelial cells and subendothelial matrix), and blood proteins (clotting factors) are all essential.
What is the sequence of events in hemostasis?
- Vascular injury triggers vasoconstriction. 2. Platelets form a hemostatic plug. 3. Tissue factor activates the coagulation cascade. 4. Secondary hemostasis forms a fibrin clot. 5. Clot retraction and clot dissolution (fibrinolysis).
Why is vasoconstriction important in hemostasis?
Vasoconstriction reduces blood flow to the injured area, helping to limit blood loss.
What role do platelets play in hemostasis?
Platelets form a temporary plug at the site of injury to stop bleeding, especially in smaller vessels.
What is the function of tissue factor in hemostasis?
Tissue factor activates the coagulation cascade, leading to the formation of fibrin, which strengthens the clot.
What is secondary hemostasis?
Secondary hemostasis is when platelets and clotting factors interact to form a fibrin clot, stabilizing the hemostatic plug.
What is the importance of clot retraction and dissolution?
Clot retraction helps to stabilize the clot and reduce bleeding, while clot dissolution (fibrinolysis) removes the clot once the injury has healed.
How do blood vessels regulate hemostasis?
Blood vessels constrict to prevent blood loss and dilate to allow proper healing and clot formation. Endothelial cells produce nitric oxide and prostacyclin to inhibit platelet aggregation.
What is the role of von Willebrand factor (vWF)?
vWF is released from endothelial cells during vascular injury and helps platelets adhere to the damaged blood vessel wall.
How is clot lysis controlled?
The fibrinolytic system, involving plasminogen, plasmin, and tissue plasminogen activator (t-PA), degrades the clot after it has formed, preventing excess clotting and allowing healing.
What is the role of plasmin in clot lysis?
Plasmin, activated from plasminogen, breaks down fibrin and dissolves the clot to restore normal blood flow.
What are fibrin degradation products (FDPs) and D-dimers?
FDPs are the byproducts of clot breakdown, and D-dimers are specific markers of fibrin degradation, often elevated in clotting disorders or excessive clotting activity.
