Basis Female Anatomy

Pictures say a thousand words... in this case body parts.

Menstruation

Averages 28 days in length.
During menstruation, the endometrial lining of the uterus is shed, thus the discharge of blood and tissue.
On average, women lose about ¼ cup of blood each month.
Day 1 of the menstrual cycle is the first day of bleeding.
Menstruation is considered an endocrine process, meaning it is controlled by hormones.

During the first half of the cycle, FSH is released causing the maturation of the egg in one of the ovaries prior to ovulation.
The egg is located in a special part of the ovary called a follicle, which secretes estrogen.
Each month, estrogen stimulates the growth of a new endometrial lining where the fertilized egg can implant.

Ovulation

Half way through the cycle, LH causes the release of the egg from the follicle. This is ovulation, and may cause a brief, sharp pain on one side of the abdomen.
Increased vaginal mucus or spotting may occur at or near the time of ovulation.
In a 28 day cycle, ovulation occurs on day 14 (the days before and after ovulation are the most fertile days).

After ovulation (2nd half of cycle), there is an increase in estrogen and progesterone, which may be responsible for premenstrual tension.
After releasing the egg, the follicle is now called a corpus luteum, which continues to secrete hormones.
The egg enters the fallopian tube, waiting to be fertilized (it takes 6 days for the egg to get to the uterus).
At the end of the cycle, the corpus luteum stops producing estrogen and progesterone if pregnancy has not occurred.
This decrease in hormones causes the blood to stop nourishing the uterine lining, and menstrual bleeding begins.
The low production of estrogen stimulates the pituitary gland to produce FSH, thus beginning the next menstrual cycle.

Fertilization

Fertilization occurs with the union of the male sperm and the female egg in the fallopian tube.
It takes about 6 days to travel down the fallopian tube where it is then implanted in the uterine wall.
With the implantation about a week after ovulation, the placenta begins to develop.
The placenta then begins to produce the HCG hormone, which prevents menstruation from occurring.
HCG also stimulates the corpus luteum to continue producing estrogen and progesterone for the first 3 months of life, after which production is taken over by the placenta.