Dependence of lag time on shear rate is determined by the factor VII activation by factor Xa. (a) Lag time as a function of wall shear rate in the range of shear rates of 0-27 s-1. The channel was 1 mm wide, and the activator was 1 mm long. The lines show: 1) normal plasma (black); 2) all zymogens (factors II, V, VII, VIII, IX, X, XI, PC, Fibrinogen) do not move with the flow (red); 3) all enzymes (factors IIa, Va, VIIa, VIIIa, IXa, Xa, XIa, PCa) do not move with the flow (blue); 4) no convection of all enzymes except for factors IIa and Xa (magenta); 5) no convection of factors IIa and Xa only (dark cyan). As can be seen from these curves, the dependence is predominantly determined by the convection of factors IIa and Xa. (b) Lag time as a function of wall shear rate without factor IIa-dependent reactions. The lines show: 1) normal plasma (black); 2) no factor IIa-dependent reactions except for fibrinogen cleavage (blue); 3) no factor VII-TF complex activation by factor Xa (red). It can be seen that the factor Xa-dependent activation of the factor VII-TF complex plays a critical role in the formation of the non-linear response of blood coagulation to flow.