The fine structure of the human ovarian hilus cells.

The ovarian hilus cells from a female patient, 77 years of age, have been observed by light and transmission electron microscopy. The ovarian hilus contains some collagenous fibers, blood vessels and nerve fibers. Hilus cells with a polygonal shape are found in clusters or scattered in the ovarian hilus. The nuclei are nearly round and contain dominant nucleoli. The most prominent cytoplasmic organelle of the hilus cell is an extensively developed smooth endoplasmic reticulum (ER) which is characteristic of steroid secreting cells. The form of the smooth ER is either a network of randomly interconnected tubules or parallel, concentric lamella. A large number of mitochondria with tubular cristae, well-developed Golgi complexes, lipid droplets and lipofuscin granules are in this cell. In addition, rod-shaped crystalline structures, similar to Reenke's crystal, are frequently observed. This fine structure indicates that the ovarian hilus cells are quite similar to steroid producing cells, especially mature Leydig cells in the human testis. The hilus cells are located near myelinated or unmyelinated nerve fibers. The ovarian hilus cells and myelinated nerve fibers may have an intimate relationship. In the interstitial tissue there are abundant capillaries with fenestrated endothelial cells. This observation indicates that the ovarian hilus cell has an important endocrine function even at an old age.