Ovulation is a fundamental process that plays a vital role in the reproductive system of individuals with ovaries. Knowing about ovulation is essential, whether you are trying to conceive, avoid pregnancy, or simply gain a better understanding of your body!
You may ask, what is ovulation? Ovulation is the phase in the menstrual cycle when a mature egg is released from one of the ovaries. The fertile window spans about six days, including the day of ovulation and the five days following. Sperm can survive in the female reproductive tract for up to five days, but the egg is only viable for approximately 12-24 hours after release.
The egg travels to the entrance of the fallopian tube. Fertilization of an egg with sperm usually takes place in the fallopian tube which connects the ovary to the uterus. If fertilization occurs, the fertilized egg, now a blastocyst, travels and implants itself in the uterus, where it begins to grow. This process often results in pregnancy. If pregnancy does not occur, the egg disintegrates and is shed along with the uterine lining during menstruation.
The occurrence of ovulation is regulated by a complex group of hormones. The first hormone is called Follicle-Stimulating Hormone (FSH), which is produced by the pituitary gland and stimulates the growth of ovarian follicles, each containing an immature egg. Secondly, Luteinizing Hormone (LH), also produced by the pituitary gland, triggers the release of the mature egg from the follicle. Thirdly, Estrogen is produced by the growing follicles and helps both thicken the uterine lining and signal the pituitary gland to release more LH. Finally, progesterone is involved in preparing the uterine lining for implantation after ovulation.
There are three phases in the ovulation process: the follicular phase, the ovulatory phase, and the luteal phase. Let me tell you a little bit about each one!
The follicular phase is the first step of the menstrual cycle where growth of the follicles in the ovaries are stimulated by FSH. Most likely, one follicle becomes dominant and matures at a faster rate than the other follicles. The ovulatory phase takes place midway through the cycle and is where LH triggers ovulation. The mature egg is released from the follicle and travels down the fallopian tube. The luteal phase is the last phase of the ovulation process. A collection of cells, called the corpus luteum, forms on an ovary during each menstrual cycle. The corpus luteum forms from the dominant follicle and releases progesterone, causing the endometrium to thicken and provides the nutrients the blastocyst needs to grow and develop. If the egg is not fertilized, the corpus luteum breaks down, progesterone levels drop, and menstruation begins.
Sources:
C. C. medical. (2024, August 22). Conception: Fertilization, Process & When it happens. Cleveland Clinic. https://my.clevelandclinic.org/health/articles/11585-conception
UCSF Health. (2024, May 21). The menstrual cycle. ucsfhealth.org. https://www.ucsfhealth.org/education/the-menstrual-cycle
Monis, C. N. (2022, September 12). Menstrual cycle proliferative and follicular phase. StatPearls [Internet]. https://www.ncbi.nlm.nih.gov/books/NBK542229/