Stereological analysis of syncytiotrophoblast from human mature placenta.

Syncytiotrophoblast from human term placenta, studied by stereological methods both by light and electron microscopy, was shown to account for 19.49% of the placenta volume. Significant differences in volume density were observed in syncytiotrophoblast from villi obtained from different regions of the cotyledon. These differences may be caused by the heterogeneous conditions of oxygenation in the intervillous space blood and its effect on trophoblastic growth. The volume density of the organelles, related to syncytioplasm volume, was 0.0524, 0.0122, 0.0033 and 0.1136, for mitochondria, lysosomes, Golgi complex and endoplasmic reticulum, respectively. There were no differences in the volume densities of the different organelles among the four cotyledonary regions studied.