Coagulation Process
- Vasoconstriction: Endothelial cells release vasoconstrictor substances like endothelin and thromboxane, reducing blood flow to the site of injury.
- Platelet activation and platelet plug formation: Platelets bind to collagen, release granules containing ADP, serotonin, and thromboxane A2, and form a platelet plug.
- Coagulation cascade: Two pathways (contact activation and tissue factor) lead to fibrin formation and the formation of a stable blood clot.
- Fibrin clot formation: Thrombin converts fibrinogen into fibrin, which forms a clot that temporarily seals the wound.
- Hemostasis stages: Vasoconstriction, platelet activation and plug formation, coagulation cascade, fibrin clot formation, and clot retraction and resolution.

Coagulation Factors
- Coagulation factors are enzymes called serine proteases.
- Tissue factor, FV, FVIII, and FXIII have different structures and are exceptions to the serine protease rule.

Coagulation Pathways
- Tissue Factor Pathway (Extrinsic): TF-FVIIa complex activates FIX and FX, leading to thrombin burst and fibrin formation.
- Contact Activation Pathway (Intrinsic): FXIIa converts FXI into FXIa, which activates FIX and forms the tenase complex.
- Final Common Pathway: Thrombin converts prothrombin to thrombin, which converts fibrinogen to fibrin, activates Factors VIII and V, and forms crosslinks in fibrin polymers.

Role in Immune System and Cofactors
- Coagulation system physically traps microbes, increases vascular permeability, and acts as chemotactic agents for phagocytic cells.
- Calcium, phospholipids, and vitamin K are required for coagulation factor complexes and their functions.

Medical Assessment and Role in Disease
- Medical tests assess coagulation system function, including aPTT, PT, fibrinogen testing, platelet count, and platelet function testing.
- Coagulation defects can cause hemorrhage or thrombosis, and platelet and coagulation factor disorders can lead to bleeding or impaired clotting.
- Pharmacology: Procoagulants, anticoagulants, and their uses in various medical conditions.
- History: Theories, discoveries, and nomenclature related to coagulation factors.