Structure and epithelial features
The inner surface of the cervical canal is lined with a single-layer columnar epithelium. Epithelial cells produce mucopolysaccharides, forming a mucus plug in the cervical canal.
The junction between the columnar and stratified squamous epithelium ("transformation zone") is of clinical significance: 90% of cervical diseases originate here. The topography of this junction varies depending on the woman's age and physiological status:
- In girls, adolescents, and pregnant women, the border is located on the vaginal portion of the cervix; this is considered a physiological process.
- In reproductive age, the junction is located at the level of the external os.
- In postmenopause, the epithelial border shifts into the cervical canal at various levels.
What passes through the cervical canal?
The cervical canal is involved in establishing communication between the fallopian tube, uterine cavity, and vagina in certain pathological conditions. In primary fallopian tube cancer, blood and tumor breakdown products flow through the uterus and cervical canal into the vagina. This causes early clinical manifestations—pathological vaginal discharge, most often serosanguineous, though serous, seropurulent, and less commonly "meat-water" discharges are also possible.
During an inevitable abortion, a completely detached ovum descends into the lower parts of the uterus, including the cervical canal.
Clinical significance and pathologies
- Cervical ectopia (pseudo-erosion): displacement of the columnar epithelium onto the vaginal portion of the cervix. In areas of ectopia, cervical glands are identified instead of stratified squamous epithelium.
- Cervical canal cancer: in the early stages, clinical symptoms are scant. Diagnosis is difficult because the cervical canal is inaccessible for colposcopy. In advanced disease, the cervix becomes barrel-shaped and firm in consistency.
- Cervical incompetence (isthmic-cervical incompetence): in the case of a complete intrauterine septum extending into the cervical canal, preserving the cervical part of the septum is recommended to prevent secondary cervical incompetence.
- Illegal (unsafe) abortion: can be performed by introducing foreign bodies or chemical solutions into the cervical canal or uterine cavity; it is life-threatening due to the high risk of infection and hemorrhage.
Instrumental procedures
The cervical canal is involved in diagnostic and therapeutic gynecological procedures:
- Before inserting an intrauterine contraceptive, bacterioscopic examination of smears from the vagina, cervical canal, and urethra is mandatory; the prerequisite for insertion is grade I–II cleanliness of smears.
- During fractional diagnostic curettage of the uterine mucosa with hysteroscopy in children, Hegar dilators up to No. 8–9 are inserted into the cervical canal, after which the endometrial scraping is obtained using a small No. 2 or 4 curette.
- If the retrieval threads are missing or detached during IUD removal, the procedure is performed strictly in a hospital setting: IUD localization is verified by ultrasound, and removal is performed after cervical canal dilation under hysteroscopic control.
- If there are changes in the cytological picture of the cervical canal or echographic signs of pathology, an advanced examination is indicated: hysterocervicoscopy, curettage of the cervical canal with histological examination of the scraping, and cone biopsy of the cervix.
Class and exam questions
Why is cervical canal cancer difficult to diagnose in the early stages?
Clinical symptoms in early stages are scant, and the cervical canal is inaccessible for colposcopy. If cytological changes or echographic signs of pathology are present, an advanced examination is indicated.
What happens to the cervical canal during an incomplete abortion?
Bimanual examination reveals cervical dilation: the cervical canal easily admits a finger. Softish tissue—remnants of the ovum, the lower pole of which may protrude into the vagina—can be palpated in the cervix.
Where is the normal junction of squamous and columnar epithelium located?
In women of reproductive age, it is located at the external os. In girls, adolescents, and pregnant women, it is on the vaginal portion of the cervix, which is considered a physiological process. In postmenopause, the junction shifts into the cervical canal at various levels.
What else to study on this topic
- Cervical ectopia
- Cervical cancer
- Intrauterine contraceptives (IUCs)
- Spontaneous abortion (miscarriage)
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