The fine structure of the surface epithelium of the human ovary.

The surface epithelium has been studied on human adult ovarian biopsies, one foetal ovary and an ovarian biopsy from a woman 12 weeks pregnant. In the adult, the surface of the ovary is covered by a single, patchy layer of epithelium which varies from squamous, through cuboidal to columnar in shape. Cytoplasmic projections extend into the peritoneal cavity from the free surface of the cells and their lateral borders are connected by desmosomes. The nucleus is irregular and the dense cytoplasm contains many polysomes, free ribosomes and tonofilaments. Intracellular vacuoles and extracellular channels contain materials of low to moderate density. Lipid droplets and compound aggregates are present and both coated and smooth vesicles occur in the peripheral cytoplasm. Focal degenerative changes may be seen which range from loss of density in the basal cytoplasm to complete desquamation. In pregnancy the basal surface of the epithelium is deeply infolded with an increase in cytoplasmic lipid. In the foetal ovary the entire surface is covered with an epithelium. From these studies and the work of others, it seems clear that, although the prime function of the ovarian surface epithelium is its contribution of pregranulosa cells during foetal development, many features remain which suggest that it has an important role in transport. It may also influence follicular development in the foetus and appears to have some potential for steroid metabolism. The patchiness and degenerative changes found in the adult human ovary may be related to fluctuations in hormonal balance.