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The female reproductive system has many functions. The ovaries produce the eggs (oocytes) that we need to reproduce. The fallopian tubes are responsible for moving the eggs to a place where they can be fertilized by sperm and once fertilized transport the newly formed embryo into the uterus. Finally, the uterus provides an environment where the developing embryo can implant and grow into a fetus until it is ready to deliver. If pregnancy does not occur the uterus sheds its lining in preparation for the next reproductive cycle and the process begins again. This cycle is driven by hormones and as a woman ages the body produces decreasing amounts until the reproductive cycle ends.
The reproductive system is made up of external and internal structures. The external genitals are referred to as the Vulva. They include:

• Labia majora: Translated this means “Large lips.” The labia majora are comparable to the scrotum in males. They protect the other external organs and contain sweat and oil-producing glands.
• Labia minora: Translated this means “Small lips.” The labia minora surround the openings of the vagina and the urethra.
• Bartholin’s glands: These glands are found next to the vaginal opening and produce a mucus secretion.
• Clitoris: The labia minora meet at the clitoris, a sensitive protrusion comparable to the penis in males.
• Urinary meatus: Opening of the urethra that connects to the bladder and carries urine outside the body.
  

The internal female reproductive organs include:

Vagina: This is a muscular canal (also known as the birth canal) that joins the cervix (lower part of the uterus) to outside the body. It is about three to five inches long and the walls contain mucous membranes that keep it protected and moist. The vagina receives sperm during sexual intercourse from the penis. It also provides the route for menstrual blood to exit the body.

Uterus: The uterus is also referred to as the womb. It is divided into two parts: the cervix, or neck of the uterus, and the body or corpus. The cervix is the lower, narrow portion where it joins with the top end of the vagina. The cervix allows sperm to enter the uterus and during menstruation, the cervix stretches open slightly to allow the blood to exit. This stretching may be the reason some women feel cramping during their menstrual cycles. During childbirth, contractions of the uterus will dilate the cervix up to 10 centimeters (almost 4 inches) to allow the child to pass through.

The main portion of the uterus is hollow and pear-shaped; the top portion is called the fundus. The uterus provides an environment that allows an embryo to implant and grow and expands to hold a developing baby. It also allows for the inner lining of the uterus (endometrium) to build up until a fertilized egg is implanted, or to shed during menses if a pregnancy did not occur.

Fallopian tubes: There are two fallopian tubes or oviducts. Each tube attaches to a side of the uterus and connects to an ovary. The fallopian tubes are narrow, about the width of a strand of spaghetti. At the end of each fallopian tube is an area with finger-like extensions called fimbria that picks up the egg released from the ovary during ovulation. Once the egg is in the fallopian tube, tiny hairs in the lining called cilia help move the egg toward the uterus. The developing egg cell takes four to five days to travel down the length of the fallopian tube. The egg is fertilized by sperm in the tube and the fertilized egg or embryo then travels to the uterus and implants in the uterine wall where it will continue to grow and develop. If the embryo doesn't make it to the uterus and implants in the fallopian tube, it is called an ectopic or tubal pregnancy, a condition that requires immediate medical attention.

From egg to embryo: Fertilization and Implantation. From the Merck Manual of Medical Information – Second Home Edition, p. 1436, edited by Mark H. Beers. Copyright 2003 by Merck & Co., Inc., Whitehouse Station, NJ.
Available at: www.merck.com/mmhe/ sec22/ch257/ch257c.html. Accessed September 2007. Please visit all of the Merck Manuals free online at www.MerckManuals.com

Human reproduction involves a complex interaction between the reproductive organs and other parts of the body that control their development and how well they function. The hormones that drive the monthly process necessary for reproduction are secreted by the hypothalamus gland, the pituitary gland and others. The hypothalamus gland secretes gonadotropin-releasing hormone (GnRH) which in turn stimulates the pituitary gland to secrete follicle stimulation hormone (FSH) and luteinizing hormone (LH). These hormones act on the ovaries and stimulate the growth of the eggs as well as the production of estrogen and progesterone. After childbirth, the hypothalamus stimulates the pituitary gland to secrete prolactin the hormone necessary for milk production in the breasts. Imbalances in hormone production can lead to infertility so if you suspect you may have a problem schedule an appointment with your health care provider.

For information about the menstrual cycle see Fertility Basics in the December 2005 newsletter available at: http://www.fertilityjourney.com/support/news/articles/
fertilitybasics/24122005.asp

For more information about hormones and hormonal imbalances go to: http://www.fertilityjourney.com/aboutfertility/femaleinfertility/
hormonalimbalance/index.asp

References:
Cleveland Clinic Health System: The Female Reproductive System. Available at: http://www.cchs.net/health/health-info/docs/2400/2418.asp?index=9118

The Merck Manual Online Medical Library. BioIology of the Female Reproductive System. Available at: http://www.merck.com/mmhe/sec22/ch241/ch241a.html