uterus
The uterus is a muscular organ shaped like an upside-down pear. It has a thick lining of tissues called the endometrium . The lower, narrower end of the uterus is known as the cervix . The uterus is where a fetus grows and develops until birth. During pregnancy, the uterus can expand greatly to make room for the baby as it grows. During birth, contractions of the muscular walls of the uterus push the baby through the cervix and out of the body.