Cervix is the lower constricted part of uterus. It is divided into two portions:
1. Upper supravaginal portion
2. Lower vaginal portion
The supravaginal portion communicates with body of uterus through internal os (orifice) of cervix. The vaginal portion of cervix projects into the anterior wall of the vagina and it communicates with vagina through external os (orifice) of cervix.
The mucous membrane of supravaginal portion of cervix has many glandular follicles, which secrete mucus. The mucus membrane of vaginal portion is formed by stratified epithelial cells.