Preferred Label : Extrinsic Prothrombin Activation Pathway;
Alternative definition : BIOCARTA: Blood coagulation takes place in 3 essential phases. The first phase is
the activation of a prothrombin activator complex. The second phase is the activation
of prothrombin. The third stage is clot formation as a result of fibrinogen cleavage
by activated thrombin. The prothrombin activation complex is formed by two pathways
each of which results in a different form of the prothrombin activator. The extrinsic
mechanism of prothrombin activator formation begins with trauma to vascular walls
or extravascular tissues. The damaged tissue releases tissue thromboplastin also known
as tissue factor (TF). The formation of a clot by this mechanism usually takes as
little as 15 seconds. This cascade is initiated by the activation of factor X by TF
and factor VII. Activated factor X combined with factor V, factor VII and TF constitutes
the prothrombin activator. Calcium (Ca ) is required for each of these steps. The
prothrombin activator in the extrinsic pathway is very similar to the activator in
the intrinsic pathway. Antithrombin III inhibits the activity of thrombin and also
the step leading to the activation of factor X. Antithrombin III is a hundred to a
thousand times more effective when bound by heparin. Protein C is activated by thrombin
and with the Protein S cofactor provides a strong negative feedback in this phase
of clot formation. (This definition may be outdated - see the DesignNote.);
NCIt note : The BIOCARTA Definition (ALT_DEFINITION) for this pathway concept was provided by
BioCarta. This property was not created by, nor is it maintained by the NCI Thesaurus
staff. Additionally, BioCarta is no longer updating its pathway data; thus, the BIOCARTA
Definition might be outdated or inaccurate. Please see the Terms and Conditions for
Use at http://www.biocarta.com/.;
Biocarta ID : h_extrinsicPathway;
Origin ID : C39076;
UMLS CUI : C1517079;
Semantic type(s)
- has_gene_product_element
- pathway_has_gene_element
