The Association of Endoplasmic Reticulum and Mitochondria in Placental Cells 1

Summary A characteristic complex of mitochondria and endoplasmic reticulum occurs in the yolk sac epithelium of carnivores and guinea pigs, and in the cytotrophoblastic cells of Langhans in the human placenta. In this complex, ribosomes are located predominantly on the cisternal membrane facing the mitochondrion. The significance of this complex is discussed briefly with respect both to protein synthesis and to fetal physiology.