On the rounded extremity of the vaginal portion of the cervix is a small, depressed, somewhat circular aperture, the external orifice of the uterus (or ostium of uterus, or external os), through which the cavity of the cervix communicates with that of the vagina.

The external orifice is bounded by two lips, an anterior and a posterior, of which the anterior is the shorter and thicker, although, on account of the slope of the cervix, it projects lower than the posterior.

Normally, both lips are in contact with the posterior vaginal wall.

See also

• Internal orifice of the uterus

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