Electron microscopy of tertiary villus (human placenta, early pregnancy)

At the left (A), part of a tertiary (terminal) villus with the multinucleated syncytiotrophoblast cell (1) (STC) at the top. The apex shows protrusions and extensive microvilli of varying sizes (brushborder). Nuclei (1a) are sectioned at different levels and the cytoplasm contains abundant organelles, endoplasmic reticulum, vacuoles and dense-stained lysosomal structures. Below a single row of desmosomes (d)-linked, electron-light cytotrophoblast cells (CTCs or Langhans cells, 2, 2a) ) close adhered to the STC. At (3) loose embryonic connective tissue. The right micrograph (B) demonstrates a higher magnification of two adjacent CTCs with nuclei (2a) and their organelle-rich cytoplasms. Remarkable is the presence of glycogen granules (arrow) and at (6) lysosomal structures. (1 in B) indicates basal part of an STC. (3) embryonic connective tissue and a continuous basal lamina (bm).