The fine structure of the developing follicle of the rhesus ovary

Abstract

In young follicles of the rhesus monkey ovary the oocyte is in direct contact with a single layer of follicle cells, which may be as little as 0.05 μ in thickness, and which in turn is enclosed by a basement membrane. As the follicle develops, the follicle cells proliferate and the zona pellucida forms between them and the oocyte. The zona pellucida has a dual structure, being homogeneous adjacent to the oocyte, but containing a flocculent, electron dense material adjacent to the follicle cells. Microvilli project from the surface of the oocyte, and cytoplasmic processes from the follicle cells penetrate the zona pellucida to terminate at desmosomes on the surface of the oocyte. Occasionally follicle cell processes penetrate deeply into the cortex of the oocyte. The mitochondria of the oocyte are found to exist in two interconnected forms—a filamentous type with numerous transverse cristae, and a larger round type with few or no cristae. Numerous Golgi bodies are found arranged peripherally in the oocyte just below the cell membrane. The endoplasmic reticulum consists of scattered smooth vesicles. After the formation of the zona pellucida, structures designated as cortical granules appear beneath the oolemma. The cytoplasm of the follicle cells contains centrioles and well developed Golgi bodies. These observations are discussed in relation to the ovaries of other mammals.