(A) Click to view.
(B) Click to view.
(A) Reserve cells in the transformation zone are continuous with the basal cells of the ectocervix and may undergo columnar and squamous metaplasia. Photomicrographs at bottom depict (from left to right) quiescent subcolumnar reserve cells, reserve cells undergoing columnar differentiation, reserve cells undergoing squamous metaplasia and ectocervical squamous epithelium (right).
(B) Schematic of the development of the cervical transformation zone.