Final answer:
The intrinsic or contact pathway of coagulation is activated by internal factors leading to clot formation through a series of reactions involving clotting factors. It merges with the extrinsic pathway, which is triggered by tissue damage, into the common pathway culminating in a blood clot. Calcium ions and vitamin K are essential in the synthesis of clotting factors.
Step-by-step explanation:
Intrinsic and Extrinsic Coagulation Pathways:
The event intrinsic or contact pathway of coagulation is part of the complex process the body uses to form blood clots. The intrinsic pathway is initiated by internal factors within the bloodstream, such as the activation of factor XII (Hageman factor), which responds to damage from conditions like arterial disease or contact with foreign materials. This pathway activates a series of clotting factors including factor XI, IX, and VIII which, along with platelet-released chemicals, accelerates the reactions leading to the activation of factor X. Subsequently, factor X enters the common pathway, which concludes the coagulation cascade resulting in the formation of a fibrin clot.
The extrinsic pathway, on the other hand, is activated by external tissue damage and starts with the release of factor III (thromboplastin). It is a quicker response pathway that also leads to the activation of factor X. Both the intrinsic and extrinsic pathways merge into the common pathway where fibrinogen is converted into fibrin, solidifying the clotting process.
During coagulation, the common pathway is the final coagulation pathway activated either by the intrinsic or the extrinsic pathway, culminating in the production of a blood clot. Important factors in this process include calcium ions and vitamin K, necessary for the synthesis of several clotting factors primarily secreted by the liver and platelets. This sequence of events is crucial in maintaining hemostasis, the cessation of bleeding, within the body.