Figure 2.

(a and b) An E9.5 FVII^+/–/TFPI^δ/δ embryo (a) surrounded by its yolk sac. The larger vitelline vessels are not readily apparent; the arrow points to a blood lake. An E9.5 normal-appearing FVII^–/–/TFPI^δ/δ embryo (b) surrounded by its yolk sac. The arrow points to a vitelline vessel in the normal-appearing yolk sac. (c–e) H&E staining of E9.5 yolk sacs. A FVII^–/–/TFPI^δ/δ yolk sac section (c) comparable in appearance to a wild-type yolk sac. A FVII^+/+/TFPI^δ/δ yolk sac (d) blood lake that contains red blood cells and further degeneration (e), with separated yolk sac endoderm (E) and mesoderm (M) layers resulting in a lack of red blood cells in the disrupted vasculature. H&E staining (f) of an E10.75 FVII^+/+/TFPI^δ/δ yolk sac showing further degeneration of endoderm and mesoderm contact and resulting anemia. (g–j) H&E staining (g) of an E10.75 FVII^+/+/TFPI^δ/δ yolk sac blood lake and antifibrin(ogen) staining of the parallel section (h), demonstrating fibrin deposition (gold) lining the interior of the blood lake. H&E staining of a vessel within the corresponding embryo (i) and corresponding antifibrin(ogen) staining of the adjacent section (j), demonstrating fibrin deposition lining the interior of the vessel.