Coagulation and fibrinolysis 1 - the coagulation cascade

What are the three pathways involved in the coagulation cascade?

Intrinsic, extrinsic, and common

What is the factor nomenclature?

Each factor has a common name and a roman numeral

• Example: Factor V

When a factor is activated, it receives an “a” after the roman numeral

• Example: Factor XII into XIIa

What is factor I common name? What is its activated name (Ia)?

Fibrinogen, fibrin

What is factor II common name? What is its activated name (IIa)?

Prothrombin, thrombin

What is factor III common name?

tissue factor, or TF

Where are the coagulation factors produced?

Liver

What cofactor is typically required for factor activation?

Calcium

How do we activate the intrinsic pathway?

When a negatively charged surface (sub-endothelial surface, phospholipid membrane) touches factor XII (12)

What happens when factor XII touches a negative surface?

XII converts into XIIa

After XII is converted to XIIa, what happens?

1. XI converts to XIa

2. XIIa cleaves prekallikrein into kallikrein

3. XIIa converts plasminogen into plasmin

What cofactor is required in factor XII activation after kallikrein is formed?

HK

What factor does XIa activate?

IX into IXa

What is the function of IXa?

form the factor Xase complex with platelet phospholipid membrane, calcium, and factor VIIIa

What does factor VIII circulate in a complex with?

vWF

What are two functions of vWF?

1. induce platelet adhesion

2. bind to VIII to prolong its half life

How does the extrinsic pathway activate?

vessel injury

What factor is present on non-vascular surfaces when a vessel injury happens?

Tissue factor

What happens when TF comes into contact with factor VII?

converts it into VIIa

What factors make up the extrinsic Xase complex?

VIIa, TF, and calcium

What is the activation step for the common pathway?

activation of factor X following either intrinsic or extrinsic pathway cascades

Which factors are involved in the common pathway?

X, V, I, II, III

When factor X is activated into Xa, what does it complex with to form the prothrombinase complex?

factor Va, calcium, and a phospholipid surface

What does the prothrombinase complex activate?

activates prothrombin into thrombin

What does thrombin activate?

fibrinogen conversion into fibrin

XIII conversion to XIIIa

What is the function of XIIIa?

to crosslink fibrin

What factors are involved in the extrinsic pathway?

VII, TF

What factors are involved in the intrinsic pathway?

XII, XI, IX, VIII

Which factor has the shortest half life?

VII