Human Reproduction

Female Reproductive System

The uterus, or womb, is a muscular chamber about the size and shape of a pear. This is where a fertilized egg can implant and mature as a pregnancy progresses. The developing baby receives its nourishment from the mother while inside the uterus.

The cervix is the opening through which sperm can enter to fertilize an egg and through which a baby leaves the uterus.

The vagina is the passage between the uterus and the outside of the body. This is the canal through which a baby is delivered and where the penis is placed during sexual intercourse.

The ovaries are two walnut-size structures located on either side of the uterus. Each holds thousands of tiny egg follicles--clusters of cells that contain an immature egg. The ovaries also produce hormones.

The fallopian tubes connect the ovaries and the uterus. About four inches long, they each begin at an opening on either side of the uterus and end in a funnel that surrounds each ovary. Each tube is thin and narrow, no wider than the head of a pin.

Ovulation

About once a month, the endometrium, or lining of the uterus, begins to thicken in preparation to receive and nourish a fertilized egg. Meanwhile, several egg follicles begin to mature, but usually only one develops fully, with a mature egg inside. It moves to the surface of the ovary, and the follicle ruptures, releasing the egg into the fallopian tube. This process is called ovulation.

Over the next few days, the sides of the fallopian tube squeeze periodically, pushing the egg down into the uterus. If the egg is not fertilized during this time it will disintegrate in the uterus. Since the thickened uterine lining is no longer needed, it will be shed over a period of three to eight days. This discharge, containing blood and other secretions, is the menstrual flow, or a "period." The time interval from one period to the next is called the menstrual cycle.

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Dive Deeper

• The following links are at the Epigee site or are recommended:
• Why is My Period Late?: Common reasons for menstrual cycle distrubances
• Menstruation: Everything you ever wanted to know about your period
• The following links are provided as an informational resource or counterpoint and are not necessarily endorsed by the author:
• Cervical Changes during the Menstrual Cycle: Photos from three women
• Women's Links: Health links and organizations for women
• The Museum of Menstruation
• The Museum of Contraception History