Pathophysiology of Hemostasis

Question 1

Step 1 Hemostasis

Answer 1

Vasoconstriction
Direct injury
Chemical messengers from endothelial cells and platelets
Initiation of the pain reflex

Question 2

Step 2 Hemostasis

Answer 2

Platelet plug formation
Injury to the vascular endothelium
VonWillebrand factor is released 
Platelets are activated by vWF
Proteins on platelets bind with fibrinogen causing platelets to adhere

Quick temporary solution

Question 3

Hemostasis Step 3

Answer 3

Secondary hemostasis (coagulation)

Clotting pathway is activated by either a defect in the vessel endothelium or disruption in the vessel wall.

Question 4

Regulatory mechanisms are in place to limit clot growth

Answer 4

Removal of clotting factors
Inhibition of activated clotting factors
Antithrombin III
Protein C  inactivates V and VIII
Protein S breaks down fibrin into fibrin degradation 
tPA
Heparin

Question 5

Platelets

Answer 5

Life span is 5-10 days

Contain serotonin, calcium, ADP, PDGF and other enzymes

Production regulated by thrombopoietin

Question 6

Nutritional deficiencies that alter the ability to control hemostasis

Answer 6

Calcium helps to activate multiple clotting factors throughout the entire coagulation cascade.

Vitamin K is required for synthesis of four clotting factors (II, VII, IX, X).

Most of the clotting factors are synthesized in the liver. (Except V and VIII)