The cervix is a tubular pathway between the vagina and the uterine body, measuring around 2–3 centimeters in length. The cervix produces mucus, which changes during the menstrual cycle to act as a barrier or a transport medium to sperms dependent on the viscosity of the mucus. During pregnancy a cervical mucus plug is formed that seals the cervical canal.
Microscopically, the cervix consists mainly of fibromuscular tissue, rich in connective tissue and blood vessels and interspersed with smooth muscle. It is covered with two types of epithelium:
The squamocolumnar junction is the boundary where these two epithelia meet. It is near this boundary that the human papillomavirus (HPV) infects cells of the cervix.