The cervix is a cylinder-shaped neck of tissue that connects the vagina and uterus. The cervix is made of cartilage covered by smooth, moist tissue, and is about 1 inch across. There are two main portions of the cervix:
- The part of the cervix that can be seen from inside the vagina during a gynecologic examination is known as the ectocervix. An opening in the center of the ectocervix, known as the external os, opens to allow passage between the uterus and vagina.
- The endocervix, or endocervical canal, is a tunnel through the cervix, from the external os into the uterus.
The overlapping border between the endocervix and ectocervix is called the transformation zone.
The cervix produces cervical mucus that changes in consistency during the menstrual cycle to prevent or promote pregnancy.
During childbirth, the cervix dilates widely to allow the baby to pass through. During menstruation, the cervix opens a small amount to permit passage of menstrual flow.