Different Phases of the Menstrual Cycle
The Normal Length of a Menstrual Cycle
It may seem strange, but not all women menstruate once a month. The average length of a cycle is 28 days, but since this can vary from 21 to 35 days, those with shorter cycles menstruate more than once a month on average in a year, while those with longer cycles menstruate less than once a month on average in a year.
Menstrual Phase
The menstrual phase is actually the time of monthly bleeding. The first day of the menstrual phase is the first day that bleeding begins, which is also considered the first day of the menstrual cycle. Menstrual blood is shed from the inner wall of the uterus, called the endometrium. It then exits the cervix and passes out of the body through the vagina. Menstrual blood can be bright red, pink, or even brown. The menstrual period usually lasts between 3 and 7 days. The total amount of bleeding in a normal period is about 20 ml.
Follicular Phase
In this phase, the hormone estrogen causes the inner lining of the uterus to grow. This lining of the uterus, called the endometrium, holds the fertilized egg in case of pregnancy. On the other hand, the increase in another hormone called FSH causes the growth of ovarian follicles. There is one egg inside each follicle. At the end of the follicular phase, only one active follicle remains. At the same time, the endometrial layer thickens as estrogen increases. Estrogen levels peak in the days leading up to ovulation. The rise in estrogen triggers the release of another hormone called LH, which causes the follicle to rupture and release the egg.
Ovulation Phase
Ovulation is when a mature egg is released from a follicle in the ovary and enters the nearest fallopian tube. Sometimes two eggs mature at the same time in a month. A sudden surge in LH causes ovulation. The egg then travels to the uterus. If your menstrual cycle is 28 days long, ovulation usually occurs on day 14. Although women have different monthly cycles.
Ovulation generally occurs 11 to 16 days before the start of bleeding. During the 3 to 4 days that the egg travels down the fallopian tube, the endometrial lining continues to thicken. If fertilization is to occur, it must occur within 24 hours of ovulation, or the egg will be destroyed.
After the ovulation phase ends, the luteal phase begins.
Luteal Phase
After ovulation, the follicle becomes the corpus luteum, which is itself a hormone-secreting organ. The corpus luteum cells secrete estrogen and high levels of progesterone to maximize the hormonal stimulation for thickening of the endometrium. If pregnancy does not occur, the corpus luteum is destroyed about 2 weeks after ovulation. In this way, progesterone levels drop and the stimulus necessary for the endometrium to remain stable is lost. As a result, the endometrium begins to break down and a new menstrual cycle begins. The destruction of the corpus luteum stops when the egg is fertilized. 5 days after fertilization, the fertilized egg enters the uterus and implants in the endometrium. After implantation, the cells that later become the placenta begin to secrete the pregnancy hormone, or HCG. The secretion of this hormone actually disrupts your monthly cycle by stimulating the corpus luteum and continuing to secrete progesterone. In this way, the endometrium is not destroyed and the pregnancy continues.
All About Eggs
- A woman releases about 400 mature eggs during her lifetime.
- The number of eggs remaining in the ovaries at any one time depends on the person’s age.
- A 20-week-old female fetus in the womb has the most eggs, about seven million.
- Most of the eggs are released before the fetus is born.
- At birth, the number of eggs remaining is reduced to two million.
- The ovaries continue to lose eggs until puberty.
- When you start puberty, you will have about 300,000 to 500,000 eggs in your ovaries.
