What is Menstrual Cycle?
Menstruation is the part of the menstrual cycle, the process that helps a woman’s body get ready for the possibility of pregnancy each month. The average cycle is 28 days long and starts on the first day of a period. The menstrual cycle can range from 21 days to 35 days. The brain pituitary gland, uterus cervix, ovaries, fallopian tubes and vagina all work together to make the menstrual cycle happen. The ovaries produce two important hormones, progesterone and estrogen. The pituitary gland also produces hormones, follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
Girls usually start menstruating around the age of 13, sometimes even younger and will continue having monthly periods until the age of 50 when the process of menopause begins. Menstrual cycles vary from one woman to the next – some may be short while others may experience longer cycles.
A typical menstrual cycle is 28 days and the length is calculated by counting the first day of menstruation as day one. Teens often experience long cycles of up to 45 days but it becomes more regular in your 20’s and 30’s lasting between 21 and 35 days. As you get older, particularly in your 40’s, the menstrual cycle becomes more regular until you reach menopause.
There are various phases of the menstrual cycle – menstruation, the follicular phase, ovulation and luteal phase.
Menstruation is known as the first part of your cycle and day 1 is the first full day of menstrual bleeding. The thickened lining of the uterus begins to shed to get ready for the new cycle. Bleeding occurs because the egg was not fertilized in the previous cycle. A menstrual period can last between 3 and 5 days, sometimes more or less. During the first three days you may experience most of your blood loss as well as symptoms such as pain in the abdominal area and your back.
During the follicular phase, the pituitary gland releases follicle stimulating hormone which helps to stimulate the growth of about 5 to 20 follicles. Each follicle consists of an egg but only one of these follicles will mature into an egg while the other stimulated follicles die. The follicle stimulating hormone causes the lining of the uterus (endometrium) to grow in preparation for the possibility of pregnancy This usually occurs around day 10 of a 28 day cycle.
The ovulation phase occurs during the middle of the cycle, around day 14 of a normal 28 day cycle when the egg leaves the ovary. During the follicular phase, an increase in the level of the sex hormone estrogen occurs as a result of the ripening follicle. When enough estrogen is produced, it sends a signal to the pituitary gland that the egg is ready to be released. The pituitary gland produces luteinising hormone (LH) and as a result ovulation is triggered. The egg is transported into the fallopian tube until it meets with the sperm for fertilization.
The end of the ovulation phase is marked by the start of the luteal phase. It lasts between 10 to 16 days. When fertilization of the egg takes place, the follicle called the corpus luteum releases the egg. This follicle produces the hormone, progesterone which helps to facilitate and maintain the thickened uterine lining. The corpeus luteum dies (around day 22 of a normal 28 day cycle) if pregnancy does not occur. As a result, the menstrual cycle is repeated.