Menstruation and the Menstrual Cycle
The menstrual cycle involves a series of changes that passes through the body of the woman. These changes are governed by the female hormones estrogen and progesterone produced in the ovaries by the body. The menstrual cycle is repeated over many years, from puberty to menopause, except when interrupted if pregnancy occurs.
In the menstrual cycle can identify two phases: the follicular and luteal, both divided by the phenomenon of ovulation.
The follicular phase begins on the first day of menstruation and ends at the time of ovulation. During this phase the pituitary gland begins to secrete a hormone that travels through the bloodstream to act on the ovaries, which favors the development and maturation of a follicle. This is called an ovarian follicle because the follicle develops, where the future egg.
The follicle grows and matures when ruptures and releases an egg. During this phase, changes occur inside the uterus to prepare it for nest egg if it is fertilized with sperm. The cervix secretes or produces large amounts of mucus to facilitate their arrival from the vagina to the fallopian tubes where it will meet the egg.
Ovulation is the release of eggs from the ovary. This takes at most 36 hours, during which it can be fertilized, otherwise, it disintegrates and is resorbed.
Ovulation begins the luteal phase in which the “scar” left on the ovary of the area where the egg is released into what is called the corpus luteum. The corpus luteum produces large amounts of progesterone that promotes the accumulation of nutrients for the fertilized egg has to nourish if fertilization is presented.
Progesterone also causes the mucus secreted by the cervix becomes thick, which prevents the entry of sperm into the uterus. The egg is picked up by the fimbriae of the fallopian tubes. If the egg is fertilized (now called egg), adheres or nest in the endometrium, the brain sends signals to continue producing the hormones necessary for pregnancy to take its course. If fertilization does not occur, the corpus luteum dies and to stop producing hormones, these levels drop sharply and approximately 10 days later, the tissues that accumulate inside the uterus is shed.
It is considered a menstrual cycle since the first day of bleeding (day 1) until the first day of bleeding of the next cycle. While the average is 28 days per cycle, is considered normal 21-day short course and long cycles of up to 35 days.