New coagulation cascade

A fascinating topic!

The coagulation cascade, also known as the blood coagulation pathway, is a complex process by which blood forms clots to stop bleeding after an injury. The cascade involves a series of enzyme-mediated reactions that ultimately lead to the formation of a fibrin clot.

Here's an overview of the new coagulation cascade:

Initiation

  1. Tissue factor (TF) is exposed to the bloodstream, usually as a result of injury to blood vessels or tissues.
  2. Factor VIIa (FVIIa) binds to TF, forming a complex that activates Factor IX (FIX).

Intrinsic pathway

  1. Factor IXa (FIXa) activates Factor VIII (FVIII) to form a complex with Factor IXa.
  2. Factor VIIIa (FVIIIa) activates Factor X (FX) to form a complex with Factor IXa.
  3. Factor Xa (FXa) activates Factor V (FV) to form a complex with Factor VIIIa.

Extrinsic pathway

  1. Factor VIIa (FVIIa) activates Factor IX (FIX) to form a complex with Factor VIII (FVIII).
  2. Factor IXa (FIXa) activates Factor X (FX) to form a complex with Factor VIIIa (FVIIIa).

Common pathway

  1. Factor Xa (FXa) activates Factor II (FII) to form a complex with Phospholipid (PL).
  2. Factor IIa (FIIa) (thrombin) converts Fibrinogen (Fg) to Fibrin (Fb).

Fibrin clot formation

  1. Fibrin (Fb) polymerizes to form a fibrin clot.
  2. Platelets aggregate to the fibrin clot, reinforcing its strength.

Regulation

  1. Antithrombin (AT) inhibits Thrombin (FIIa) and Factor Xa (FXa).
  2. Protein C (PC) and Protein S (PS) inhibit Thrombin (FIIa) and Factor VIIIa (FVIIIa).
  3. Tissue factor pathway inhibitor (TFPI) inhibits Factor VIIa (FVIIa) and Factor IXa (FIXa).

This new coagulation cascade is a simplified representation of the complex process of blood coagulation. It highlights the key players and reactions involved in the formation of a fibrin clot.