Academic literature on the topic 'Oocyte degeneration'

The production of germ cells is essential for the continuation of a species. In the female this function is accomplished by the ovaries. In addition, the ovaries secrete steroids and nonsteroidal hormones that not only regulate the secretion of anterior pituitary hormones but also act on various target organs, including the ovaries themselves, the uterus, fallopian tubes, vagina, mammary gland, and bone. Morphologically, the ovary has three regions: an outer cortex that contains the oocytes and represents most of the mass of the ovary; the inner medulla, formed by stromal cells and cells with steroid-producing characteristics; and the hilum, which, in addition to serving as the point of entry of the nerves and blood vessels, represents the attachment region of the gland to the mesovarium. The cortex, which is enveloped by the germinal epithelium, contains the follicles, which are the functional units of the ovary. They are present in different states of development or degeneration (atresia), each enclosing an oocyte. In addition to the oocyte, ovarian follicles have two other cellular components: granulosa cells, which surround the oocyte, and thecal cells, which are separated from the granulosa cells by a basal membrane and are arranged in concentric layers around this membrane. The follicles are embedded in the stroma, which is composed of supportive connective cells similar to that of other tissues, interstitial secretory cells, and neurovascular elements. The medulla has a heterogeneous population of cells, some of which are morphologically similar to the Leydig cells in the testes. These cells predominate in the ovarian hilum; their neoplastic transformation results in excess androgen production. The ovary produces both steroids and peptidergic hormones. Whereas the steroids are synthesized in both interstitial and follicular cells, peptidergic hormones are primarily produced in follicular cells and, after ovulation, by cells of the corpus luteum. The initial precursor for steroid biosynthesis is cholesterol, which derives from animal fats of the diet or from local synthesis.