Ultrastructure of primordial germ cells in human embryo.

Electron microscopic studies of the primordial germ cells were performed on 6 human embryos between 26 and 31 days post conceptionem. These cells were found in the intestitial tissue of the dorsal mesentery or in the genital ridge. They were round to spindle in shape and occasionally extended cytoplasmic processes. The round nucleus displayed centrally located prominent nucleoli and the cytoplasm contained abundant glycogen particles, mitochondria of vesicular type, bundles of tonofilaments and occasional lipid droplets.