Hematoxylin and eosin–stained sections of the ventral abdominal wall of E17.5 fetuses. (A and B) Images of the same WT (A) and KO (B) fetuses shown in Fig. 4 at higher (20-fold) magnification depecting that the panniculus carnosus (arrowheads) was less well developed and discontinuous, and that the rectus (1) and transversus abdominis (2) were thinner and hypotrophic in KO. Myofibers could be discerned in the transversus abdominis. (C and D) Images of the ventral abdominal wall of another KO at 1.25-fold (C) and 5-fold (D) magnification, showing that the external (3) and internal (4) oblique muscles were present. The mesodermal sac that had contained the herniated gut was preserved in this fetus. We pushed the herniated gut gently into the abdominal cavity before dissecting the skin flap. (E and F) 1.25- and 5-fold magnification of a HET showing the umbilical cord and that all five muscles were well developed and the myofibers were oriented similar to WT. Representative images of two WT, four KO, and two HET fetuses.