What is the Normal Structure of the Cervix?

The cervix is the opening of the uterus. The outside of the cervix and the vagina are covered by a layer of flat cells called squamous cells. When a Pap smear is taken, some of these cells are scraped off to be examined under a microscope. The canal of the cervix is lined by tall column-like cells columnar cells.

Somewhere on the cervix the two cell types, squamous cells and columnar cells, meet at a place called the squamo-columnar junction. This junction may be on the outside of the cervix where it is easy to see or within the cervical canal where it may be difficult to see. The squamo-columnar junction is also called the transformation zone because the tall columnar cells are constantly being transformed into flat squamous cells. It is in this transformation zone that abnormal growth or dysplasia develops.

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