The uterus–aka the womb–is a muscular organ nestled between the rectum and the bladder. Shaped like an upside-down pear, the uterus is in charge of reproduction in women. It works to feed and contain a fertilized egg until the fetus is carried to term, ready to be born.
Structure-wise, the uterus is divided into four regions:
- The fundus is the broad, curved upper portion where the fallopian tubes and the uterus meet.
- The body is the uterus’s fundamental section, and it begins right below the fallopian tubes’ level and extends downward until the uterine cavity and walls start to become more narrow.
- The isthmus is the narrow region that’s below the fundus and body.
- The cervix runs from the isthmus until it becomes the vagina.
The uterine cavity extends into the vaginal cavity; together, the two consist of what is colloquially known as the birth canal. The uterine cavity is lined by the endometrium, which is a moist, mucous membrane. During the menstrual cycle, the endometrium’s lining changes in thickness; it’s at its thickest during ovulation, or when the egg is being released from the ovaries. The endometrium also makes secretions in an attempt to help both the egg and sperm cells stay alive. If the egg is fertilized, it latches on to the endometrial wall and starts to develop and grow. On the other hand, if it’s unfertilized, the wall sheds its outermost layer of cells. The egg and extra tissue then leave the body through menstruation.
The uterine wall itself consists of three layers of muscular tissue. If one is pregnant, the uterine wall continually becomes thinner as it expands along with the continued pregnancy. The uterus reverts back to its original size about six to eight weeks after birth. And when a female is born, her uterus remains small until she hits puberty, at which point it quickly grows to its adult shape and size. After menopause, the uterus shrinks, and becomes more pale and fibrous.
All three of the Ezra scanning packages offer a look into the uterus; you can learn more about our plans here.