1. Stage 1: Platelet Plug Formation
   1. Platelets adheres to exposed collagen
      1. By activating multiple factors needed to form fibrinogen bridges between glycoprotein IIb/IIa on adjacent platelets
   2. Adhesion--> Platelet activation --> Platelet aggregation= Platelet plug *Plug is unstable and needs fibrin
2. Stage 2: Coagulation
   1. Production of fibrin to reinforce platelet plug
      1. Figure 55.2
      2. 2 Pathways
         1. Extrinsic (Tissue Factor Pathway)
            1. Activated by trauma to vascular wall--> Fibrin Formation
         2. Intrinsic (Contact Activation Pathway)
            1. Activated when blood makes contact with collagen that has been exposed as a result of trauma to blood vessel wall--> Fibrin Formation
         3. Both pathways go through factor conversions then converge at factor Xa Same final series of reactions occur in the pathways
            1. Factors Xa & Va convert prothrombin (II) to thrombin (IIa)
            2. Thrombin (IIa) converts fibrinogen to fibrin
            3. Clot formed that reinforces initial platelet plug
            4. Side note:
            5. Deep Vein Thrombosis (DVT) Occurs at bifurcations of deep veins If not treated, major risk is pulmonary embolism (PE) OR Afib causing stroke/MI