Tags: Anatomical Structure.
The external orifice of the uterus (or ostium of uterus or external os) is a small depressed somewhat circular aperture on the rounded extremity of the vaginal portion of the cervix. Through this aperture the cervical cavity communicates with that of the vagina. The external orifice is bounded by two lips an anterior and a posterior. The anterior is shorter and thicker though it projects lower than the posterior because of the slope of the cervix.
