Final answer:
The Graafian follicle, or mature ovarian follicle, is characterized by several features including secondary follicles, a fluid-filled antrum, an oocyte in meiosis, granulosa and theca cells, and hormonal changes during the follicular phase, culminating in ovulation. Post-ovulation, it turns into the corpus luteum in the luteal phase.
Step-by-step explanation:
The Graafian follicle, also known as the mature ovarian follicle, goes through several stages of development, which are collectively referred to as folliculogenesis. Here are the seven features that characterize a mature Graafian follicle:
- Secondary follicles, which develop from primary follicles and contain a primary oocyte with multiple layers of granulosa cells.
- Accumulation of fluid in the cavity (antrum), which separates the granulosa cells, leading to the formation of a large, fluid-filled cavity called the antral or tertiary follicle.
- An oocyte that is arrested in the first meiotic division within the follicle.
- The presence of granulosa cells that produce estrogen and are critical for the oocyte’s nutrition and development.
- The development of theca cells (thecal layers) outside the granulosa cells, which also contribute to estrogen production.
- The follicular phase of the ovarian cycle during which the follicle matures in response to follicle-stimulating hormone (FSH).
- Ovulation, where, stimulated by a surge in luteinizing hormone (LH), the mature follicle ruptures, releasing the oocyte for potential fertilization.
After ovulation, if there is no fertilization, the follicle that housed the ovulated egg transforms into the corpus luteum during the luteal phase of the menstrual cycle. The corpus luteum secretes hormones such as progesterone to prepare the endometrium for a possible pregnancy.