The uterus is a hollow, thick-walled, pear-shaped muscular organ about 3in. long, situated in the pelvis cavity between the rectum and the bladder. Three parts of the uterus can be distinguished: (1) the body, or corpus uteri, with its superior expanded portion called the fundus extending above the entrance of the uterine tubes; (2) the isthmus, or middle, slightly constricted portion; and (3) the cervix, or cylindrical lower part, that surround the cervical canal and projects into the vagina. The short (2.5-cm) cervical canal extends from the intenal orifice, or os, of the uterus to the external os at the termination of the cervix.
The cavity of the uterius is small because of the thickness of its walls. The part of the cavity within the body is triangular and has three openings, one very small one at each upper angle communicating with the fallopian tubes, and the third, the internal os, opening into the cervical canal. The uterus is the organ of the reproductive tract in which the embryo grows and develops until the time of delivery.
