Ovarian Stroma

As with the male counterpart, the ovaries are derived from the genital ridge later descending to their final position in the pelvis. In adults, the ovaries have an ovoid shape and are usually 3-5cm long. They are a layered structure with an outer layer germinal epithelium, tunica albuginea, cortex and medulla that is innermost (fig. 1). Although now challenged by recent discoveries (1), the germinal epithelium; a continuation of the peritoneum, is inaptly named due the mistaken belief that germ cells arise from this surface layer. Instead germ cells are more likely to arise from the gonadal tissue itself (2). Spindle shaped cells called the ovarian stroma constitutes the major cell type ubiquitous throughout the body of the ovary. In the periphery, …show more content…
To start off with, the mitotic proliferation phase of completes in the neonate to produce primordial germ cells (fig.1, 2) that subsequently enter meiosis. These cells then arrest at the first meiotic prophase (4) to become the primary oocytes situated within the primordial follicle. Once left the pool of primordial follicles, the primordial follicle will then grow in a gonadotropin-independent manner (5) acquiring a distinct single layer of granulosa cells which signifies the primary follicle (fig. 1b.). Next, the primary follicle acquires multiple layers of granulosa, a zona pellucida and theca interna which signifies the secondary follicle. It is these structures that start to express the luteinizing hormone receptor (LHR) (5). At this stage follicle stimulating hormone receptors (FSHR) are also expressed and the secondary follicle undergoes gonadotropin-dependent growth through the effects of both follicular LHR and FSHR activation (4). The secondary follicle progressively gains a follicular antrum (fig. 2.a) which undergoes expansion mediated by luteinizing hormone (LH) …show more content…
2.b) synthesize oestrogen precursors and androgens in an LH dependent manner. The granulosa binds FSH which stimulates granulosa-mediated aromatization of androgens to estrogens (4). Acting with FSH androgens stimulate proliferation of granulosa cells, causing follicular growth. There is then a positive feedback loop by oestrogens that stimulate granulosa proliferation which produce more oestrogen. As a result, this causes a large increase in circulating eostrogen which can also be detected in urine and used as a marker to the state of maturity of the most mature follicles