Ovulation

Ovulation happens approximately midway through the menstrual cycle after the follicular phase. The length of a typical menstrual cycle and the date of the last menstrual period can be used to calculate the days when a woman is most fertile. Menstrual flow does not occur when an ovum is fertilised by a sperm, indicating pregnancy. During the follicular phase, the first follicles in the ovary mature into fully grown Graafian follicles. Proliferation is the process through which endometrial regenerates. Changes in pituitary and ovarian hormones result in the formation of Graafian follicles and endometrial regeneration.

Process of Ovulation:

Ovulation happens approximately midway through the menstrual cycle after the follicular phase. The length of a typical menstrual cycle and the date of the last menstrual period can be used to calculate the days when a woman is most fertile. The days preceding ovulation are the most fertile (about days 10 to 18 of a 28-day cycle). The average time from the start of the last menstrual period (LMP) to ovulation is 14 days, however, this varies significantly across females and between cycles within a single female, with a 95 percent prediction interval of 8 to 20 days.

Stages of Ovulation:

During this stage, the release of gonadotropins such as luteinizing hormone and follicular stimulating hormone steadily increases, boosting follicular development as well as oestrogen secretion by the increasing follicles.

• LH and FSH levels peak in the middle of the cycle, around the 14th day.
• The rapid secretion of LH, which peaks in the mid-cycle and is known as the LH surge, causes the rupture of the Graafian follicle and, as a result, the release of the ovum, which is known as ovulation.
• During the luteal phase, the ruptured Graafian follicle transforms into a yellow body known as the Corpus luteum.
• The corpus luteum secretes a large amount of progesterone hormone, which keeps the endometrium healthy and ready for the fertilised ovum to implant.
• During pregnancy, all menstrual cycle events stop and there is no menstruation.
• In the absence of fertilisation, the corpus luteum degenerates, leading the endometrium to dissolve, resulting in menstruation and the beginning of a new cycle.
• Menstrual cycles in humans terminate at the age of 50, which is known as menopause.

Menstrual Cycle and Ovulation:

The usual menstrual cycle is divided into two parts: a 14-day follicular phase in which the endometrium proliferates, and a 14-day luteal phase in which the uterine lining sloughs off. Thus, ovulation on the one hand and menstruation on the other separate the two stages. The phases might last anywhere from a few days to several weeks in various women, and even within the same woman. Cycle duration variations are most common in the first few years after menarche (the first menstrual cycle) and just before menopause (when menstruation ceases).

The fluctuating levels of oestrogen and progesterone in the blood during the menstrual cycle have several additional repercussions. Basal body temperature fluctuates modestly during the follicular phase of the menstrual cycle but increases considerably the following ovulation. 

This spike correlates with the postovulatory rise in blood progesterone levels and is caused by progesterone’s influence on the brain’s temperature-regulating centres. Changes in mood and activity, as well as an increase in fluid retention, may occur as blood estradiol and progesterone concentrations fall approach the conclusion of the cycle. The symptoms of premenstrual syndrome are caused by a decrease in estradiol and progesterone secretion, however, the link between hormonal changes and these symptoms is unknown.

During menopause, the ovaries shrink and are typically composed of ancient fibrous tissue. The production of oestrogen declines but does not stop completely.

Ovulation Induction:

Ovulation induction is a promising assisted reproductive therapy for people suffering from polycystic ovarian syndrome (PCOS) and oligomenorrhea. It’s also used in IVF to help the follicles mature before the egg is extracted. Ovarian stimulation is frequently used in conjunction with ovulation induction to enhance the formation of a large number of oocytes.

Conclusion:

In this unit, we learnt about the process of ovulation which is the release of the ovum from the ovary. Ovulation happens approximately midway through the menstrual cycle after the follicular phase. The length of a typical menstrual cycle and the date of the last menstrual period can be used to calculate the days when a woman is most fertile. The days preceding ovulation are the most fertile (about days 10 to 18 of a 28-day cycle).