the columnar mucus-secreting epithelium of the endocervix meets the squamous epithelial covering of the exocervix at the external os; thus, the entire "exposed" cervix is covered by squamous epithelium
in most young women, there is distal growth of the columnar epithelium that extends beyond the exocervical os, a condition called ectropion; thus, the squamocolumnar junction comes to lie visibly on the exocervix
The region in which this takes place is known as the transformation zone
Frequently, overgrowth of the regenerating squamous epithelium blocks the orifices of endocervical glands in the transformation zone to produce small nabothian cysts.