Anti-fibrin(ogen) staining of E18.5 embryonic tissues. (A) Brain of TFPI_K1(−/−) embryo. Arrows denote two small vessels with apparent fibrin thrombi. (B) Brain of TFPI_K1(+/−) embryo. (C) Diffuse anti-fibrin(ogen) staining within the interstitia of the liver of a TFPI_K1(−/−) embryo. (D) Liver of TFPI_K1(+/−) embryo.