endocervix

The endocervix is the inner portion of the cervix that lines the cervical canal, running from the internal os, where the uterus communicates with the canal, to the external os at the vaginal opening. It is the glandular, mucosa-covered part of the cervix on the uterine-side of the transformation zone.

Histology and structure: The endocervical mucosa is lined by tall simple columnar epithelium that forms abundant mucus-secreting glands (endocervical glands). The stroma contains connective tissue and smooth muscle fibers. The transformation zone, where the epithelium of the endocervix transitions to the squamous epithelium of the ectocervix, is clinically important because it is the area most exposed to sampling during cervical screening.

Function and physiology: The endocervical mucus is produced by the endocervical glands and plays a role in lubrication and protection of the upper reproductive tract. The viscosity and properties of the mucus are modulated by hormonal changes across the menstrual cycle, with estrogen promoting more watery mucus around ovulation to facilitate sperm passage and progesterone producing thicker mucus at other times for protection.

Clinical relevance: The endocervix is a key site in cervical cancer screening, as the transformation zone and endocervical canal are commonly sampled during Pap tests. Pathologies affecting the endocervix include endocervical polyps, infections (such as from sexually transmitted pathogens), and inflammatory conditions. Lymphatic drainage from the endocervix typically reaches regional pelvic nodes.