Compare the mechanism of the activation of the intrinsic and extrinsic pathway of coagulation.
The intrinsic pathway activates through substances "intrinsic in the blood" and act on factor XII (hageman's factor).
The extrinsic is activated through factor VII.
What are the three major groups of bleeding disorders?
- platelet related
- clotting factor related
Which bleeding disorders are caused by vascular diseases?
- mechanical trauma
- vessel wall weakness
- immune mechanisms
What is thrombocytopenia, and what is its clinical significance?
plt < 70,000
Bleeding occurs 10-20,000.
may occur b/c of decreased production, increased destruction, removal, or utilization.
What are the main causes of thrombocytopenia?
aplastic anemia (loss of all hematopoietic cells)
leukemia (normal replaced with tumor cells)
drugs damaging megakaryocytes
What is thrombasthenia?
defective platelet aggregation
What is hemophilia, and how is it diagnosed?
a X-linked recessive congenital clotting factor deficiency
Typically prolonged aPTT. PT and bleeding time are normal.
Why is hypofibrinogenemia a sign of a chronic liver disease?
All of the proteins of the coagulation cascade are synthesized by liver cells, except vWF, which is from endothelial cells.
Fibrinogen represents the most abundant of these factors, therefore a deficiency means chronic liver disease.
Why is disseminated intravascular coagulation accompanied by a bleeding tendency?
Injured endothelial cells release thrombogenic stimuli into the blood. Consumption of coagulation factors occurs during the formation of thrombi. Blood is depleted of coagulation factors. As the clots are dissolved, blood rushes to the newly reopened vessles, but bleeding occurs because there are no more coagulation factors.
Which coagulation test measures the intrinsic and extrinsic pathway.
PT = extrinsic and common
aPTT = intrinsic and common
What are natural anticoagulants?
Vitamin K is used to synthesize which clotting factors?
II, VII, IX, X