Two kinds of epithelia may cover the cervix: (1) shiny pink squamous epithelium, which resembles the vaginal epithelium, and (2) deep red, plushy columnar epithelium, which is continuous with the endocervical lining. These two meet at the squamocolumnar junction. When this junction is at or inside the cervical os, only squamous epithelium is seen. A ring of columnar epithelium is often visible to a varying extent around the os—the result of a normal process that accompanies fetal development, menarche, and the first pregnancy.*
With increasing estrogen stimulation during adolescence, all or part of this columnar epithelium is transformed into squamous epithelium by a process termed metaplasia. This change may block the secretions of columnar epithelium and cause retention cysts (sometimes called nabothian cysts). These appear as one or more translucent nodules on the cervical surface and have no pathologic significance.
*Terminology is in flux. Other terms for the columnar epithelium that is visible on the ectocervix are ectropion, ectopy, and eversion.
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