The Vascular Supply of the Placenta in Normal and Abnormal Pregnancy

Abstract

Transmission and scanning electron microscopy have only recently been applied to the study of human pregnancy but the limited work already done has proved of value in elucidating the complex morphologic relationship of the uteroplacental vascular supply. The placenta has also proved to be an ideal organ for electron microscopic studies on cellular function. Most of the early observations involved the fetal part of the placenta. Here, as in other organs and tissues where structure and function are studied together, electron microscopy has increased our understanding of the cellular and syncytial elements of the placenta. New information on the nature of the “placental barrier” was obtained by using electron microscopy for functional studies of placental transport. Earlier work with light microscopy suggested that the syncytium was a simple semipermeable membrane. However, the observations of the first electron microscopists in this field showed that the syncytial trophoblast cytoplasm was too complex to behave as a passive structure for ionic and fluid transport.^4,48 Since this pioneer work extensive studies have been made of the ultrastructure and function of the human trophoblast.^{49, 50}