Computational modeling simulations recapitulate experimental results. (A) Geometries used for the computational models, shown in full (i) and deconstructed into the individual components: –vessel (ii), hemostatic plug (iii), and extravascular space (iv). Supplemental Figure 5 and supplemental Table 1 provide more detailed illustrations and dimensions. (B) Fluid velocity field (i), thrombin (ii), and APC (iii) concentration fields in the cremaster geometry model. The sheltering action of platelets allows the thrombin generated both intra- and extravascularly to diffuse through the hemostatic mass; more intravascular thrombin results in APC being generated, and the APC has increased residence time within the platelet mass. (C) Fluid velocity field (i), thrombin (ii), and APC (iii) concentration fields in the jugular geometry model. Thrombin backpropagates via diffusion through the hemostatic mass, but as soon as it diffuses out of the platelet mass, it is quickly washed away. The thrombin that diffuses through the sides of the plug produces only low amounts of APC. V_max, maximum velocity.