The Female Reproductive System

 
The female reproductive system is a combination of both the reproductive anatomy and physiological cycles associated with the female body.

Vagina: The Passageway

The anatomy of female reproductive organs begins from the bottom up with the vagina. Also known as the birth canal, this organ is tube-like in shape and approximately 2. 5 - 4 inches long. The muscular walls of the vagina create a passageway leading to the cervix. These walls become erect when a woman is aroused as extra blood is pumped into blood vessels lining the vagina. The vagina has three functions, acting as a receptacle for the penis during love-making; an outlet for blood during menstruation and as a passageway for the baby to pass through at birth.

During intercourse sperm is deposited as a seminal pool at the top of the vagina, behind the cervix.

Cervix: The Gate

The cervix is comprised of the lower one third of the uterus and extends downwards into the upper portion of the vagina. The cervix acts as a gate into the uterus, controlling sperm entry into the female reproductive tract. Depending on the menstrual cycle, the cervix can produce different types of mucus; usually the mucus is thick and impenetrable, however during ovulation it is thin, clear and nutrient-rich in order to promote fertilization.

The sperm swim through the cervical opening into the body of the uterus. The mucus produced in the preovulatory period is highly receptive to sperm. This combines with the cervixes ability to act as a reservoir by allowing the slow release of sperm into the uterus over several days. Once the sperm have moved through the uterus, it progresses into the fallopian tube where fertilization occurs in the outer one third of the tube.

Uterus: The Nest

The uterus, also known as the womb, is a hollow pear-shaped organ which houses the embedded fertilized egg (embryo) and maintains fetal development until its expulsion during labor. The uterus usually tilts forward at a ninety degree angle to the vagina, towards the bladder. However in about 20-30% of women, it tilts backwards towards the backbone. The endometrium is a nutrient rich, mucous membrane which acts a protective nest for the growth of the embryo. The thickness of the endometrium is under hormonal regulation. When the hormones withdraw from circulation at the end of the menstrual cycle, the blood supply in the uterus is cut off, allowing for shedding of the unfertilized egg and lining as waste.

During pregnancy the muscular wall of the uterus, known as the myometrium, expands from its normal size of 2-3 ounces up to 2 lbs. in order to accommodate the growing baby. These muscles are then used in contractions that promote the delivery of the fetus.

Fallopian Tubes: The Meeting Place

The fallopian tubes connect the uterus to the ovaries and are approximately the size of a juice box straw. At the end of the tubes there are tiny finger-like projections, known as fimbriae, which connect to the ovary and catch the egg as it is released by the ovary. The outer third of the fallopian tube is the site of fertilization and also serves as short-term accommodation for the newly fertilized egg.

In short, the fallopian tubes have four critical functions:
1. To move sperm to the location of fertilization.
2. To collect the egg from the ovary at ovulation.
3. To provide a hospitable environment for fertilization to take place.
4. To nourish and move the resulting embryo into the uterus.

The Ovaries: The Egg Warehouse

The two almond-shaped ovaries lie on either end of the fallopian tubes, on both sides of the uterus. Like the testes, the ovaries store sex cells, while also producing the hormones estrogen and progesterone. While a baby girl may be born with around 60,000 sex cells, only about 400 will have the chance to ripen and be fertilized in her lifetime.

Ovulation occurs normally once a month at mid-cycle, when a preovulatory follicle ruptures and releases an egg. If no pregnancy arises, the ruptured follicle, known as the corpus luteum, shrinks and follicle growth restarts. The unfertilized ovum dissolves and is flushed out of the uterus during menstruation, along with blood and other bodily fluids.

The size of the ovary can change dramatically depending on the stage of the menstrual cycle. Early on it can be the size of an almond, enlarging by 2-3 times in size as the follicle grows.

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