The portion of the cervix that projects into the vagina, the vaginal part or ectocervix, is represented by the upper two thirds of top figure. The lower third of the micrograph reveals the portion of the cervical canal (CC). Lower figure shows the continuation of cervical canal (CC). The plane of section in both figures passes through the long axis of the cervical canal which is narrowed and cone shaped at its two ends. The upper end, the internal os, communicates with the uterine cavity, and the lower end, the external os (Os), communicates with the vagina. (For purposes of orientation, realize that only one side of the longitudinal section of the cervix is shown in these
Ectocervix, uterus, human, H&E ×240.
The surface of the vaginal part of the cervix, ectocervix is covered by the stratified squamous epithelium (SSEp). The epithelium-connective tissue junction presents a relatively even contour in contrast to the irregular profile seen in the vagina.
Transformation zone, cervix, uterus, human, H&E ×240.
The mucosa of the cervical canal is covered with columnar epithelium. An abrupt change from stratified squamous epithelium (SSEp) to simple columnar epithelium (CEp) occurs within the transformation zone at the vaginal opening
Cervical glands, cervix, uterus, human, H&E ×500.
This figure shows, at high magnification, portions of the cervical gland identified in the rectangle in Figure on left. Note the tall epithelial cells and the lightly staining supranuclear cytoplasm, a reflection of the mucin dissolved out of the cell during figures and that the actual specimen, as seen in a section, would present a similar image on the other side of the cervical canal.)
The mucosa (Muc) of the cervix differs according to the cavity it faces. The two rectangles in upper figure delineate representative areas of the mucosa that are shown at higher magnification in upper right and middle right figures, respectively.
Bottom figure emphasizes the nature of the cervical glands (Gl). The glands differ from those of the uterus in that they branch extensively. They secrete a mucous substance into the cervical canal that serves to lubricate the vagina.
In other respects, the epithelium has the same general features as the vaginal epithelium. Another similarity is that the epithelial surface of the ectocervix undergoes cyclical changes similar to those of the vagina in response to ovarian hormones. The mucosa of the ectocervix, like that of the vagina, is devoid of glands.
of the cervical canal (external os). The lower rectangle in top left figure marks this site, known as the transition zone, which is shown at higher magnification here. Note the abrupt change in the epithelium at the point indicated by the diamond-shaped marker, as well as the large number of lymphocytes present in this region.
tissue preparation. The crowding and the change in shape of the nuclei (asterisk) seen at the upper part of one of the glands in this figure are due to a tangential cut through the wall of the gland as it passed out of the plane of section. (It is not uncommon for cervical glands to develop into cysts as a result of obstruction in the duct. Such cysts are referred to as Nabothian cysts.)
BV, blood vessels CC, cervical canal CEp, columnar epithelium Gl, cervical glands Muc, mucosa Os, ostium of the uterus SSEp, stratified squamous epithelium asterisk, tangential cut of the epithelial surface KEY