Hemostasis Flashcards
Define Hemostasis
The physiological processes that stop bleeding
What are the four steps that constrain bleeding?
- Physical factors
- Platelets form hemostatic plug
- Coagulation due to production of fibrin clot
- Clot retraction
What are the two physical factors that slow bleeding?
- Back Pressure
2. Vasoconstriction
Why do black eyes form?
Bleeding below eye not easily stopped
What chemicals contribute to vasoconstriction?
Serotonin
Epinephrine
Thromboxane A2
What does thromboxane do?
- Vasoconstriction
2. Platelet aggregation
What reduces uterine blood loss after birth?
Compression of blood vessels due to underlying muscles
Where is thrombopoietin produced?
Liver and Kidney
The release of platelets from bone marrow is induced by _____
thrombopoietin
What is the von Willebrand factor?
Glycoprotein that:
- Forms bridge between platelet surface receptors and collagen
- Important in platelet adhesion to wound sites
- Not an enzyme
What is the von Willebrand factor produced by?
Endothelial cells due to adherence of platelets
What other protein does the von Willebrand factor bind to?
Factor VIII
What activates thrombin?
Membrane phospholipids
What initiates a cascade that ends in clot formation?
thrombin activation
What induces factor VIII to dissociate from von Willebrand factor?
thrombin activation
Is von Willebrand factor bound to Factor VIII in normal circulation or during clot formation?
normal circulation
What does the released of ADP from ruptured cells cause?
Platelet aggregation
When ADP binds to platelet ADP receptors, what is released?
thrombin
Drugs such as _____ irreversibly inhibit the platelet ADP receptor?
Plavix
fibrin stabilizing factor is also known as _______
Factor XIII
During coagulation, thrombin cleaves ______ into ______ that assemble into ordered arrays of _____
Thrombin cleaves fibrinogen into fibrin monomers which assemble into fibrous arrays of fibrin
What does Factor XIII do?
Stabilizes and tightens polymerized fibrin by forming covalent bonds between fibrin strands
What replaces unstable platelet aggregates during coagulation?
Factor XIII
Coagulation factors are _____
serine proteases
The intrinsic pathway of the coagulation cascade is initiated by
factor XII
Does a lack of Factors XII lead to bleeding disorders?
Hell no. We don’t need no Factor XII
The extrinsic pathway of the coagulation cascade is initiated by released of ______
tissue factor:
Factor III, thromboplastin
What is tissue factor produced by?
Subendothelial tissues:
smooth muscle cells
Neutrophils
Monocytes