Ovulation and menstruation are the two different phases of the menstrual cycle. The menstrual cycle is the time period between the start of your period (the day you bleed) until the first day of your next period.
Preparing for Ovulation
At the start of each menstrual cycle, follicle stimulating hormone (FSH), produced by the pituitary gland, starts stimulating your ovaries to make mature eggs.There are fluid-filled cavities in your ovaries called follicles. Each follicle has an immature egg. The follicle stimulating hormone stimulates more than one follicles to develop and mature. Initially many follicles start to develop but eventually only one dominant follicle develops and produces a mature egg. Another hormone called estrogen is important in developing a friendly environment in the uterus, in case if you get pregnant this month. Estrogen is at its lowest levels at the start of your cycle and then starts rising with the growing follicles. High levels of estrogen also induce the production of fertile cervical mucus. The fertile cervical mucus creates a sperm-friendly environment to enhance your chances to conceive.
Estrogen levels are still increasing and eventually cause a surge of luteinizing hormone (LH). This rapid rise in LH stimulates the developed follicle to rupture and release the fully mature egg.This egg now enters the fallopian tube. This process is called ovulation.
After ovulation, the egg moves towards your uterus through the fallopian tube. Here the egg can survive up to 24 hours. Sperm can survive in the uterus for 3-5 days. So, the days leading to ovulation and the day of ovulation are most fertile days of your cycle.
Shortly after ovulation, the ruptured follicles start producing another hormone called progesterone. This hormone builds up the lining of the uterus in case if the egg is fertilized.
Preparing for Menstruation
If the egg is not fertilized, the levels of hormones progesterone and estrogen start to decline gradually. When the levels of these hormones become very low, there is nothing to maintain the lining of the uterus. The uterus starts breaking and shedding its lining. This the called menstruation. The first day you bleed is the start of your next menstrual cycle.
The length of the menstrual cycle and the day of ovulation are directly related. Because your period starts 14 days after you ovulate. The length of the cycle may vary from 21 to 42 days.