What initiates coagulation?
When the blood vessel is injured, so is the endothelium, so it releases the endothelium tissue factor (TF), which complexes with factor VII, activating it, which then activates factor X and IX and the rest of the cascade continues.Collagen is also exposed to a molecular, called high molecular weight kininogen (HMWK), prekallikrein and Hageman factor (factor XII), forming a complex. Prekallikrein is converted to Kallikrein and factor XII is activated to produced factor XIIa, which then activates factor XI and then factor X (the common factor between those two pathways), and the rest of the cascade continues, till the formation of the blood clot.