The uterus is part of the female reproductive system that exists within the pelvis. The word "uterus" comes from the Latin word for "womb." During pregnancy, the fetus — or, in the case of twins or multiples, fetuses — develops within the womb. As the fetus develops, the womb expands to give necessary room. Humans are not the only creatures that reproduce via a uterus. In fact, the uterus is the major female reproductive organ in most mammals.
On one end of the uterus is the cervix, which opens into the vagina. On the other end, the organ is connected to the fallopian tubes. There are two fallopian tubes, each of which is connected to one of the two ovaries. During ovulation, which happens once a month in female humans, ovum travel from the ovaries down the fallopian tubes and into the womb. Ovum are commonly called "eggs" in casual speech. During ovulation, if a sperm reaches the ovum in the womb, a pregnancy can result.
If a woman does not get pregnant during her time of ovulation, then she will menstruate. Menstruation is the shedding of lining of the uterine walls. During the month, the uterine walls thicken in order to prepare for a possible pregnancy. In the event that an ovum is fertilized with sperm, then the resulting embryo will become embedded in one of these thickened uterine walls. In the months that a pregnancy does not occur and an embryo does not become embedded in one of the walls, the lining will come loose and express itself through the vagina.
In most cases, the uterus is tucked up above the bladder, which is the reason why many pregnant women find that they have to urinate far more frequently than when they are not expecting. This is because the developing fetus is literally sitting on top of the pregnant mother's bladder. There are some medical conditions in which the uterine placement or angle is abnormal. Sometimes the shape of the organ is unusual. These conditions can lead to difficult sexual function and complications with pregnancies.
After puberty, the entire female reproductive system should be checked for general health by a gynecologist. A gynecologist is a doctor who specializes in the female reproductive system. Although certain reproductive issues may need to be addressed before puberty, some issues do not become apparent until after puberty or when the woman becomes sexually active.