Cervix

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The uterine cervix is the little neck thing at the end of the uterus. It has three parts, each with a distinctive epithelium: the exocervix, endocervix and transformation zone.

The exocervix consists of non-keratinized stratified squamous epithelium. It is multi-layered, and looks pale pink-tan to the naked eye. When exposed to estrogen, the exocervix's epithelium thickens and cells accumulate glycogen.

The endocervix consists of columnar mucin-secreting epithelium. It is a single layer, bright red to the naked eye.

The transformation zone (aka T zone) is not visible to the naked eye, but instead looks like the exocervix. It lies between exocervical squamous and endocervical mucinous epithelium. This is an important area to watch, since it has quite a bit of metaplasia, stimulated by the low vaginal pH that occurs after puberty, trauma, chronic irritation, or cervicitis. At menopause, the transformation zone retracts into the cervical canal as tissues atrophy.