The follicular phase, also known as the preovulatory phase or proliferative phase, is the phase of the estrous cycle (or, in primates for example, the menstrual cycle) during which follicles in the ovary mature from primary follicle to a fully mature Graafian follicle. It ends with ovulation. The main hormones controlling this stage are secretion of gonadotropin-releasing hormones, which are follicle-stimulating hormones and luteinising hormones. They are released by pulsatile secretion. The duration of the follicular phase can differ depending on the length of the menstrual cycle, while the luteal phase is usually stable, does not really change and lasts 14 days.
⭐ Core Definition: Follicular phase
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👉 Follicular phase in the context of Luteal phase
The menstrual cycle is on average 28 days in length. It begins with menses (day 1–7) during the follicular phase (day 1–14), followed by ovulation (day 14) and ending with the luteal phase (day 14–28). While historically, medical experts believed the luteal phase to be relatively fixed at approximately 14 days (i.e. days 14–28), recent research suggests that there can be wide variability in luteal phase lengths not just from person to person, but from cycle to cycle within one person. The luteal phase is characterized by changes to hormone levels, such as an increase in progesterone and estrogen levels, decrease in gonadotropins such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH), changes to the endometrial lining to promote implantation of the fertilized egg, and development of the corpus luteum. In the absence of fertilization by sperm, the corpus luteum degenerates leading to a decrease in progesterone and estrogen, an increase in FSH and LH, and shedding of the endometrial lining (menses) to begin the menstrual cycle again.
In this Dossier
- ⭐ Core Definition: Follicular phase
- 👉 Follicular phase in the context of Luteal phase
- Follicular phase in the context of Ovulation
Follicular phase in the context of Ovulation
Ovulation is an important part of the menstrual cycle in female vertebrates where the egg cells are released from the ovaries as part of the ovarian cycle. In female humans ovulation typically occurs near the midpoint in the menstrual cycle and after the follicular phase. Ovulation is stimulated by an increase in luteinizing hormone (LH). The ovarian follicles rupture and release the secondary oocyte ovarian cells.
After ovulation, during the luteal phase, the egg will be available to be fertilized by sperm. If it is not, it will break down in less than a day. Meanwhile, the uterine lining (endometrium) continues to thicken to be able to receive a fertilized egg. If no conception occurs, the uterine lining will eventually break down and be shed from the body via the vagina during menstruation.
View the full Wikipedia page for Ovulation