[An ultrastructural study of ovulatory changes in stromal tissue of the follicular apex in the human (author's transl)].

To elucidate the mechanism of follicular rupture at ovulation in human, ultrastructural changes of stromal tissue of the follicular apex during follicular growth and ovulation were studied by focusing on the collagen and fibroblasts in the stroma. Sixteen ovaries were obtained from women at their thirties who underwent the abdominal hysterectomy for gynecologic diseases. From follicles at various stages of development, apical portions were excised and processed for electronmicroscopy. At the apex of growing follicles, fibroblasts with poor cytoplasm and abundant collagen fibers among them were observed in the layers of tunica albuginea and theca externa. At the preovulatory follicles, fibroblasts had rich cytoplasm containing lysosomal granules and multivesicular structures and intercellular collagen fibers were rather sparse. These lysosomal granules and multivesicular structures in the fibroblasts were much conspicuous in the theca external layer of preovulatory and post-ruptured follicles and collagen fibers among these fibroblasts were almost disappeared. It seems that these intercellular collagen fibers and ground substance were digested by the content of lysosomal granules and multivesicular structures.