Secondary - Pt 1

What are the three major processes of hemostasis?

1. Primary hemostasis – formation of the initial platelet plug.

2. Secondary hemostasis – stabilization of the platelet plug by forming a fibrin clot.

3. Fibrinolysis – dissolution of the clot as healing occurs.

How are the three stages of hemostasis related?

They are closely interconnected and function through a series of checks and balances that regulate clot formation and clot dissolution.

The Coagulation Cascade

What is the coagulation cascade?

A sequence of coagulation reactions often viewed as two pathways that merge into a common pathway leading to fibrin clot formation.

What are the two main pathways of the coagulation cascade?

The extrinsic pathway and the intrinsic pathway.

Into what pathway do the intrinsic and extrinsic pathways merge?

The common pathway.

What is the final goal of the coagulation cascade?

Formation of a fibrin clot.

How is the coagulation cascade commonly illustrated?

As a waterfall-like sequence of reactions.

Does the coagulation cascade occur as cleanly in vivo as it is illustrated?

No. The pathway is more complex in vivo than the simplified diagrams suggest.

Cascade Activation

How is each step of the coagulation cascade activated?

Each coagulation factor is activated into its active form, which then catalyzes the activation of the next factor in the cascade.

How are activated coagulation factors designated?

By adding the letter "a" after the Roman numeral (for example, Factor XII becomes Factor XIIa).

Why is the coagulation pathway compared to a waterfall?

Because activation of one clotting factor triggers activation of the next factor in sequence. (each pathways happens at the same time)

Pathways of Secondary Hemostasis Extrinsic Pathway

Which components make up the extrinsic pathway?

Tissue Factor (TF) and Factor VII.

Which components make up the intrinsic pathway?

• Prekallikrein (PK),

• High Molecular Weight Kininogen (HK/HMWK),

• Factors XII, XI, IX, and VIII.

Which coagulation factors belong to the common pathway?

Factors X, V, II, and I.

Which pathway forms the final fibrin clot?

The common pathway.

What is the endpoint of the common pathway?

Cross-linked fibrin that stabilizes the primary platelet plug.

Coagulation Factors

What are coagulation factor precursors called?

Zymogens.

What is a zymogen?

An inactive precursor that is converted into its active enzyme form.

How are coagulation factors generally designated?

By Roman numerals.

Which coagulation factors are commonly referred to by name instead of Roman numeral?

• Factor I (Fibrinogen),

• Factor IIa (Thrombin),

• Factor III (Tissue Factor),

• Factor IV (Calcium).

How is an activated coagulation factor written? (is added once it is activated)

By adding the letter "a" after its Roman numeral (example: XII → XIIa).

Properties of Coagulation Factors

What is the ultimate purpose of secondary hemostasis?

To convert the unstable platelet plug into a stable fibrin clot through activation of coagulation factors