Cryofracture of human term amniochorion.

By use of cryofracture and scanning electron microscopy of human amniochorion we have captured images of all the major layers of the tissue. Correlation of confocal and electron-microscope data has allowed greater understanding of how these cellular and acellular layers interconnect in order to maintain their integrity as a multilaminar tissue. This is not straightforward as mutual sliding or area change is required of concentric curved surfaces which expand and contract as does the amnion. In this paper we suggest a mechanism by which the amnion is able to slide with respect to the chorion and still maintain continuity as a structural unit. It is based on the observation of complementary gyri and sulci on surfaces facing the spongy layer which is a shear plane. Cellular detail at higher resolution of the amniotic epithelium and acellular layers provides a more complete description of structural composition than was previously available.