On the varied appearances of the human placental villous surface visualised by scanning electron microscopy

Scanning electron microscopy enables extensive areas of the human placental villous tree to be viewed at high resolution in a relatively quick and easy manner. It is therefore an invaluable aid to the study of normal placental structure, and may have a potential role to play in pathological diagnosis. However, with increasing experience an awareness of the possible artefacts that may be introduced during fixation and tissue preparation is gradually developing. Some of these artefacts are common to other organs and applications of scanning electron microscopy, whereas others result from the unique structure and three-dimensional configuration of the placenta. Examples of the second category are poorly documented, and yet their occurrence may also significantly influence the appearance of the tissue as seen by light or transmission electron microscopy. This paper illustrates examples of this problem, and emphasises some of the factors that must be considered when interpreting both scanning and transmission electron micrographs of the villous surface.