basic anatomy and physiology of cervix to understand physiological changes in transformation zone during reproductive years, types of transformation zones and their importance

1. Anatomy and Physiology of the
Cervix
DR. ANAM RIAZ

2. Gross Anatomy
Lower one third of uterus
3-4 cm in length and 2.5 cm in diameter
Lower end projects through anterior vaginal wall, dividing it into supra
vaginal and a lower vaginal portion

3. Gross Anatomy

4. Supra vaginal part of the Cervix
Relations:
Anteriorly- base of bladder
Posteriorly- rectouterine pouch with intestinal coils and rectum
On each side-
• Ureter
• Uterine artery
• Attachment of Mackenrodt’s ligament
• Lower attached margin of the broad ligament

5. Vaginal Part of the Cervix
Conical in shape.
• Projects into the anterior wall of vagina forming the vaginal fornices
(anterior, posterior and 2 lateral).
• Cervical canal (Endocervical canal) opens into the vagina by an
opening called the external os.
• External os is small and circular in nulliparous women.
• In multiparous women, the external os is bounded by the anterior
and posterior lips.

6. Cervical os appearance in Nulliparous vs.
Multiparous women

7. Microscopic Anatomy
• The cervix is composed of epithelium (surface lining) and underlying
stroma (deeper fibrous tissue) separated by a thin barrier called basement
membrane.
• The ectocervix is lined by non-keratinized stratified squamous epithelium
that has multiple (1520) layers of cells and appears pale pink in colour.
• The squamous epithelium is divided into basal, parabasal, intermediate
and superficial layers from below upwards

9. Microscopic Anatomy
• The endocervix is lined by columnar epithelium composed of a single layer
of tall cells with dark-staining nuclei close to the basement membrane. On
visual examination, columnar epithelium appears red in colour with a
granular velvet like surface.
• The epithelium forms several invaginations into the substance of the
stroma, resulting in the formation of endocervical crypts (sometimes
referred to as endocervical glands). The crypts lined by columnar
epithelium may extend 5–8 mm into the stroma.

11. Microscopic Anatomy
• The columnar epithelium at its lower limit meets the squamous epithelium.
The junction between the two epithelia is known as the squamocolumnar
junction
• The SCJ is usually visible as a sharp border located near the external os.
• The position of the SCJ in relation to the external os changes with age,
pregnancy and use of oral contraceptive pills.

15. Physiological changes in cervical Epithelium
• The cervix enlarges under the influence of oestrogen at puberty
and during pregnancy.
• As a result, columnar epithelium becomes visible on the
ectocervix and the SCJ moves out on the ectocervix. This
condition is known as ectropion or ectopy.

16. Physiological changes in cervical Epithelium
• The columnar epithelium on the ectocervix becomes exposed to
the acidic environment of the vagina. This causes destruction of
the columnar epithelium and its gradual replacement by the
newly formed squamous epithelium. This process through
which the columnar epithelium on the ectocervix is gradually
replaced with squamous epithelium is called squamous
metaplasia.

17. Physiological changes in cervical Epithelium
• Squamous metaplasia usually begins at the SCJ at the distal limit of the
ectopy (original SCJ) and gradually moves inwards (centripetally) towards
the external os
• The SCJ formed between the metaplastic squamous epithelium and the
columnar epithelium is known as the new SCJ.
• The area between the original SCJ and the newly formed SCJ as a result
of metaplasia is the transformation zone (TZ).

18. Cervical ectopy and Squamous Metaplasia

19. Transformation Zone
• The proximal extent of the TZ is the new SCJ and is easy to identify.
Tongue like projections of the thin newly formed metaplastic squamous
epithelium is a feature of the normal TZ.
• Patent crypts appear as small openings on the TZ. Some of the crypts are
blocked by the metaplastic epithelium, which leads to formation of
retention cysts known as nabothian follicles or cysts.
• The crypt openings and nabothian cysts are features of normal TZ. The
position of the crypt opening or the nabothian cyst farthest from the SCJ
helps to identify the outer limit of the TZ

21. Changes in Transformation Zone
• During pregnancy the cervix enlarges, becomes congested and the
columnar epithelium extends to the ectocervix (ectropion). The SCJ is
easily visible on the ectocervix
• During the peri-menopausal period and after menopause, the cervix
shrinks due to the lack of oestrogen and SCJ moves inside the
endocervical canal from the external os. In post-menopausal women, the
SCJ is often invisible on visual examination.

22. Cervical changes in pregnancy and
postmenopausal