The menstrual cycle consists of four main stages:
1. Menstruation (Days 1-5)
The first phase of the menstrual cycle is at this point. If fertilization and implantation of an embryo does not occur, it starts with loss of the uterine lining (endometrium). Typically, menstrual bleeding lasts 3 to 7 days.
2. Follicular Phase (Days 1-13)
The second stage lasts until ovulation and starts on the first day of menstruation. Follicle-stimulating hormone (FSH), released at this stage by the pituitary gland in the brain, promotes the development of follicles in the ovaries. Undeveloped eggs are found within each follicle. The follicles produce estrogen as they grow, which aids in the uterine lining’s thickening in preparation for a future pregnancy.
3. Ovulation (Day 14)
The third stage, or ovulation, usually occurs on or around day 14 of a 28-day menstrual cycle. A developed egg is released into the fallopian tube by one dominant follicle. A spike in the pituitary gland’s luteinizing hormone (LH) causes this release. The most fertile part of the menstrual cycle occurs when the egg is ready for sperm fertilization.
4. Luteal Phase (Days 15-28)
The luteal phase is the last phase of the menstrual cycle. The ovary’s burst follicle develops into a structure known as the corpus luteum after ovulation. The corpus luteum produces progesterone, and maintaining the endometrium’s thickening aids in preparing the uterus for pregnancy. The corpus luteum degenerates, progesterone levels drop, and the uterine lining starts to shed if fertilization does not take place, starting the next menstrual cycle.
It’s vital to remember that cycle duration and stage length might vary depending on the person. The phases are based on a typical 28-day menstrual cycle, however, periods may be as long as 35 days or more.
For more details read: Understanding Your Menstrual Cycle: A Comprehensive Guide