Fig. 5. Defects of placental structures. Hematoxylin-Eosin staining of paraffin wax sections of deciduas (E11.5) from collagen IV-deficient (–/–) embryos and normal littermates (+/+). (A) The Reichert's membrane (RM) of collagen IV-deficient embryos appears thinner, and ruptures (arrows) are causing severe bleeding of maternal blood (arrowhead) into the yolk sac cavity. YS, yolk sac. (B) The development of the labyrinth layer of the placenta is retarded in mutant embryos (–/–) as compared to wild-type embryos (wt). The contact between maternal (open arrowheads) and embryonic blood (closed arrowheads) is reduced. Scale bar: 100 µm.