The female reproductive system is a complex system of organs and processes intended primarily for producing offspring. The external reproductive organs function to protect the internal reproductive organs and provide a structure for sperm to enter (“Female reproductive system,” 2019). The vagina, ovaries, uterus, and fallopian tubes constitute the inner part of the reproductive system, within which the generation and fertilization of female reproductive cells occur directly.
These cells, called oocytes, are formed during oogenesis, which begins during the formation of a human fetus. In the future, it is from these cells that eggs are formed during the menstrual cycle. The nature of the hormones flowing at this time is regulated by four hormones: estrogen, progesterone, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) (“Female reproductive system,” 2019). These substances take part in developing, preparing, and releasing the egg cell ready for fertilization.
The length of the menstrual cycle is usually about 28 days, during which the two cycles, ovarian and uterine, go through different phases. The ovarian cycle consists of three main components: the follicular phase, ovulation, and the luteal phase, the last of which has a distinct length of 14 days, while the former can vary in duration (Rosner et al., 2021). The follicular phase corresponds to the development of the oocyte through the action of FSH and LH hormones. Next, the ovulatory phase begins, during which the dominant egg is released, ready for fertilization. During the luteal phase, a new structure, the corpus luteum, forms, preparing the egg for fertilization. In the absence of fertilization, the lining of the uterus exfoliates and comes out together with the egg.
The uterine cycle occurs in parallel and has three phases: menses, proliferative and secretory. Menstruation coincides in its course with the final stages of the luteal phase when the shell that has become unnecessary is peeled off. Along with this, a small amount of blood is lost, and this process lasts up to 6 days. The proliferative phase coincides with the end of the follicular phase when the generation of the uterine lining occurs. In addition, in this phase, a special cervical mucus is secreted, increasing the chances of fertilization due to the greater cooperation with the sperm. Finally, the secretory phase coincides with the luteal phase and promotes the fertilized egg’s development and an increase in progesterone.
References
Female reproductive system. (2019). Cleveland Clinic. Web.
Rosner, J., Samardzic, T., & Sarao, M. S. (2021). Physiology, female reproduction. StatPearls Publishing LLC.