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Cascada de Coagulación
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Cascada de Coagulación

Hemostasis and Coagulation Mechanisms

Overview of Hemostasis

  • Damage to blood vessels activates three basic mechanisms for hemostasis: vasoconstriction, platelet adhesion, and degranulation.
  • Vasoconstriction occurs immediately to reduce blood loss; exposed collagen and von Willebrand factor facilitate platelet shape change and adhesion.

Platelet Activation

  • Degranulation of platelets releases serotonin (a vasoconstrictor), ADP, and thromboxane A2.
  • ADP attracts more platelets to the site, while thromboxane A2 promotes further platelet aggregation and vasoconstriction.
  • This positive feedback loop strengthens the platelet plug at the injury site.

Coagulation Process

  • The damaged tissue releases tissue factor (TF or thromboplastin), activating the extrinsic pathway of coagulation with calcium ions.
  • Factor XII activates Factor XI, which in turn activates Factor IX along with cofactor VIII, initiating the intrinsic pathway leading to Factor X activation.

Formation of Fibrin Clot

  • Activated Factor X interacts with Factors III, V, calcium ions, and thromboplastin to activate prothrombinase.
  • Prothrombinase converts prothrombin into thrombin; thrombin then converts fibrinogen into fibrin.
  • Fibrin forms a loose mass that stabilizes into a tight clot as red blood cells aggregate within it.

Inhibition of Platelet Aggregation

  • Aspirin inhibits thromboxane A2 synthesis through irreversible acetylation of cyclooxygenase required for prostaglandins and thromboxane production.
Video description

La cascada de la coagulación descrita en forma didáctica. Formación del coágulo a partir de la formación del tapón plaquetario, la fibrina producto de la cascada de la coagulación y los eritrocitos.