Secondary Hemostasis

Secondary Hemostasis

• response of coagulation factors to site of injury

• response of coagulation inhibitors to “check” coagulation process

End result of secondary hemostasis

stable fibrin-platelet plug

Fibrinolysis

involves the lysis of the clot formed in secondary hemostasis

Factors in Contact Family

XII, XI, PK, and HMWK

Contact Family Characteristics

requires contact with negatively charged surface for activation

Factors in Prothrombin Family

II, VII, IX, X, Protein C, and Protein S. These factors are vitamin K dependent

Prothrombin Family Characteristics

requires vit K for synthesis, needs Ca++ to bind a phospholipid surface

Factors in Fibrinogen Family

I, V, VII, and XII

Fibrinogen Family Characteristics

consumed in clotting process

Vitamin K

necessary for gamma carboxylation of II, VII, IX and X so they can bind calcium and platelet phospholipids

Intrinsic Pathway

• XII, XI, IX, VII, PK, HWMK, PL, Ca++

• activated by exposure to collagen

• required a negatively charged surface

Measures Intrinsic Pathway

aPPT assay - activated partial thromboplastin

Intrinsic Pathway Useful in Monitoring

heparin therapy (inhibits thrombin)

Extrinsic Pathway

• VII, III (TF), Ca++

• activated by release of tissue from injured cells

• TF is found in all tissue

Measures Extrinsic Pathway

PT assay - partial thromboplastin

Extrinsic Pathway Useful in Monitoring

coumadin (warfarin) therapy (interferes with vitamin K dependent factors)

Common Pathway

• X, V, II, I, Ca++ (XIII)

• final pathway of both intrinsic and extrinsic pathway

Five functions of Thrombin (IIa)

• fibrinogen → FIBRIN

• activates XIa

• XIII → XIIIa

• Enhances factors V and VIII activity

• aggregates more platelets