The internal os is the opening between which structures?

The internal os is the opening between which structures?

• A. The cervix and the uterine cavity
• B. The cervix and the vaginal canal
• C. The uterus and the fallopian tube
• D. The uterine cavity and the external os

Answer: (A)

The internal os is the opening where the uterine cavity communicates with the cervical canal, i.e., between the uterus (uterine cavity) and the cervix. The cervical canal has an upper opening into the uterine cavity (internal os) and a lower opening into the vaginal canal (external os). So this is not the connection to the vagina or to the fallopian tubes, and it’s not the junction between the uterus and the vaginal canal.

The internal os is the opening where the uterine cavity communicates with the cervical canal, i.e., between the uterus (uterine cavity) and the cervix. The cervical canal has an upper opening into the uterine cavity (internal os) and a lower opening into the vaginal canal (external os). So this is not the connection to the vagina or to the fallopian tubes, and it’s not the junction between the uterus and the vaginal canal.