transformation zone
(TRANZ-for-MAY-shun zone)
The area around the opening of the cervix where the endocervix (inner part) and ectocervix (outer part) come together. This area contains both glandular cells (cells that make mucus) from the endocervix and squamous cells (thin, skin-like cells) from the ectocervix. Most abnormal cell changes and most cervical cancers begin in the squamous cells of the transformation zone. Also called squamocolumnar junction.
Enlarge this image in new windowAnatomy of the cervix. The cervix is the lower, narrow end of the uterus that connects the uterus to the vagina. It is made up of the internal OS (the opening between the cervix and the upper part of the uterus), the endocervix (the inner part of the cervix that forms the endocervical canal), the ectocervix (the outer part of the cervix that opens into the vagina) and the external OS (the opening between the cervix and vagina). The area where the endocervix and ectocervix meet is called the squamocolumnar junction, which contains both glandular cells (column-shaped cells that make mucus) from the endocervix and squamous cells (thin, flat cells) from the ectocervix. The squamocolumnar junction is sometimes referred to as the transformation zone.