Girls
When a baby girl is born, she has all the parts of her reproductive system in place, but it isn't until puberty that she is able to reproduce. A woman's reproductive system is made up of the vulva, vagina, cervix, uterus, fallopian tubes, and ovaries.

Vagina
The vagina is a muscular, hollow tube that's about 3 to 5 inches (8 to 13 centimeters) long in a grown woman. Because it is made of muscle, it can expand and contract. Its ability to become wider or narrower allows the vagina to accommodate something as slim as a tampon and as wide as a baby.

The opening of the vagina is completely or partially covered by the hymen, a thin piece of tissue that has one or more holes in it. Hymens are often different from person to person. Most women find their hymens have stretched or torn after their first sexual experience. Some women who have had sex don't have much of a change in their hymens. If the hymen is stretched or torn, it may bleed a little, but this usually causes little, if any, pain.

Although many people use the word vagina to describe the part outside the body, the vagina is actually completely inside the body - you can't see it at all. The entire outside area that shields the vagina is called the vulva. The vulva is made up of the mons pubis, the labia, the clitoris, and the urinary and vaginal openings.

The mons pubis (pronounced: monz pew-bis) is the mound just below the abdomen. This is the area of the vulva that becomes covered with pubic hair when a girl goes through puberty. At the bottom of the mons pubis, there are two folds of skin on either side of the opening of the vagina. These are called labia (sometimes called lips). There are actually two sets of folds: the labia majora (or outer lips) and the labia minora (or inner lips). In the space where the labia minora (inner lips) meet at the bottom of the mons pubis, the lips cover a small sensitive bump called the clitoris. Below the clitoris is the urethral (pronounced: you-ree-thrul) or urinary opening, which is part of the urinary system. This is where urine leaves the body. Finally, below the urinary opening is the vaginal opening, the entryway to the vagina.

Cervix
The cervix (pronounced: sur-vix) is the narrow bottom part of the uterus that extends into the vagina. It has strong, thick walls. The opening of the cervix, which is very small - no wider than a straw - provides an entryway to the uterus. That's why a tampon can never get lost inside a girl. During childbirth, the cervix can expand to allow a baby to pass.

Uterus
The uterus (pronounced: you-tuh-rus) has thick muscular walls and looks like an upside-down pear. Normally, the size of a woman's uterus is about the same as her closed fist, and the walls of the uterus touch one another. The uterus contains some of the strongest muscles in a woman's body. These powerful muscles are able to expand and contract to accommodate a growing baby and to then help push the baby out during labor. The uterus is also where menstruation begins each month - it builds up its inner lining, known as the endometrium (pronounced: en-doe-mee-tree-um), with extra blood and tissue, anticipating that an egg might be fertilized by sperm entering the woman's body. The fertilized egg can then attach to the endometrium and pregnancy occurs. If an egg is not fertilized, the uterus sheds this extra blood and tissue, which comes through the cervix and out of the vagina as a menstrual period.

Fallopian Tubes
The fallopian (pronounced: fuh-loh-pee-un) tubes are attached on one end to either side of the uterus, and they extend out and back from the uterus. Each fallopian tube is about 4 inches long and is about as wide as a piece of spaghetti. Within each tube is a tiny passageway no wider than a sewing needle.

At the other end of each fallopian tube is a fringed area that looks like a funnel. This fringed area wraps around the ovary, but isn't completely attached to the ovary. When an egg pops out from the ovary, it enters the fallopian tube. Once the egg is in the fallopian tube, tiny hairs in the tube's lining help push the egg down the narrow passageway toward the uterus.

Ovaries
The ovaries (pronounced: oh-vuh-reez) are located about 4 or 5 inches (10 to 13 centimeters) down from a girl's waist, and each one is about the size of an almond in its shell. They are shaped like eggs and measure about 1 1/2 to 2 inches (4 to 5 centimeters) in length in a grown woman. The ovaries sit on either side of the uterus, and special tissue keeps them connected to the fallopian tubes.

Each woman's ovaries contain about 1 million ova (eggs). A baby girl is born with all these eggs, but it isn't until puberty that the eggs begin to be released. Usually, after a girl reaches puberty, one ovum (or egg) will be released from an ovary each month until she begins menopause. An egg pops out of the ovary and enters the fallopian tube, where it makes its journey to the uterus. If the egg joins with sperm in the fallopian tube and is fertilized, it will attach to the inner lining (endometrium) of the uterus and begin to develop into a baby. If the egg isn't fertilized, it is washed away along with the blood and tissue of the endometrium that grows on the inside walls of the uterus each month - otherwise known as a menstrual period.

The ovaries are also responsible for making hormones, such as estrogen and progesterone. Estrogen is a major part of puberty in girls - it is responsible for the development of breasts, female body shape, and other changes that girls go through during puberty.