What makes adolescent females so susceptible to STIs?

In all females the cervix is covered with two cell types – epithelial (skin-like) cells and columnar (like the cells lining the intestine) cells. In mature females, the outer part of the cervix (ie, the part the doctor sees when he or she looks at the cervix to obtain cells for a PAP smear) is covered with multiple layers of hardy (squamous) epithelial cells, and the upper part inside the cervical canal is lined with fragile columnar cells. Where the two cell types meet is referred to as the squamocolumnar (SC) junction.

The location of this junction varies considerably between adolescents/young females and mature females.
Adolescents/young females have a normal condition referred to as ectopy. With ectopy, the junction between the two cell types is somewhere on the outer cervix (where a physician could see it on pelvic exam) rather than inside the cervical canal. The more ectopy there is, the larger the diameter of fragile columnar cells on the outer exposed surface of the cervix. In addition to being highly susceptible to STIs, the exposed columnar and SC junction cells are more easily transformed into precancerous cells or into cancer if infected with human papillomavirus.

Reviewed : May 2016