Regional anatomy of the term human placenta.

We have studied regional anatomical variability in four term placentae, comparing both whole placental regions and intralobar zones and plates. In addition, we have emphasized the need for careful selection of the area to be sampled, rather than strictly randomized sampling of the whole placenta. A unique contribution is our quantitative data for a number of structures of the several intralobar zones and plates. The data confirm the hypothesis that the area best suited to physiological exchange is the central region parabasal plate. The relative homogeneity of the intralobar zones in this area make it a representative area for sampling for various placental studies.