In a speculum exam, the os refers to the opening of which structure?

• A. The opening of the urethra
• B. The opening of the vagina
• C. The opening of the uterus
• D. The opening of the cervix

Answer: (D)

In this context, the os is the opening of the cervix—the cervical os, or the mouth of the cervical canal. When a speculum is used, you’re looking at the cervix and its opening where the canal meets the vaginal canal. There are two related openings: the external os (between cervix and vagina) and the internal os (between uterus and cervix). The term “the os” in a speculum exam most commonly refers to the cervical os, not the urethral opening, the vaginal opening, or the opening of the uterus itself.