cervix

The cervix, or cervix uteri, is the narrow lower portion of the uterus that opens into the vagina. It is about 2 to 3 centimeters long and consists of two regions: the endocervix, containing the internal opening (internal os) and lined by mucus-secreting columnar epithelium, and the ectocervix, with the external opening (external os) covered by stratified squamous epithelium. The transformation zone is the area where these two epithelia meet and is the site where most cervical neoplasia develops.

Functions of the cervix include allowing the passage of sperm into the uterus during fertilization, producing cervical mucus whose consistency changes across the menstrual cycle to influence fertility and protection, and forming a mucus plug during pregnancy to help protect the uterus. During labor, the cervix dilates and effaces to enable childbirth.

Clinical relevance: The transformation zone is the primary site for cervical dysplasia and cancer. Screening programs use the Pap smear and human papillomavirus (HPV) testing to detect precancerous changes. Abnormal results may lead to follow-up with colposcopy, biopsy, or therapeutic procedures such as loop electrosurgical excision procedure (LEEP) or cone biopsy. Other conditions affecting the cervix include cervical insufficiency in pregnancy, infections, polyps, and congenital anomalies.

Anatomy and supply: The cervix receives blood from branches of the uterine arteries and drains through the uterine and vaginal veins, with lymphatic drainage to regional nodes. Nerve supply is autonomic.