Placental structure and fetal membranes. (A,B) Macroscopy, near-term placenta. Sac-like hemophagous organ (Ho) central to the zonary placenta (Zp) and supplied by an area of destruction (circle) in the uterus (Ut). Am = amnion, ft = fetus. (C) Scanning electron microscopy, mid gestation hemophagous organ. The hemophagous organ (Ho) was near the labyrinth (Lab), separated by a thin membrane (arrow). (D) Pearl’s iron staining, mid-gestation. Iron deposits in the cytoplasm of the trophoblast (arrows). (E,F) Hematoxylin and eosin, near term. Villi of the hemophagous organ with a columnar trophoblast (Tb) and fetal vessels (Fv). (G) Macroscopy, term. The yolk sac (Ys) was surrounded by the amnion (Am). The umbilical cord (UC) was short. (H) Pearl’s iron staining, mid-gestation, with iron deposits in the yolk-sac endodermal cells (arrows). Am = amnion. (I) Masson’s trichrome, near term. Histology of the yolk sac, with mesothelium (me), mesoderm (m), and columnar endoderm (ce) with vacuoles (arrows).