The Normal Cervix

Teresa M. Darragh, M. D., UCSF, Depts. Of pathology & Ob/GYN

Fuente: The Normal Cervix
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Normal Cervix

Anatomic Landmarks

  • Fibro-muscular cylinder, 3 x 5 cm
  • Exocervix
  • External os
  • Endocervical canal
  • Internal os

Normal cervix

  • Size and shape of the cervix varies:
    • Age
    • Hormonal status
    • Parity

Exocervix

  • Ectocervix
  • Portio vaginalis
  • Anterior and posterior lips
  • Vaginal surface of the cervix
  • Extends from the external os to the vaginal fornix

External Os

The external opening of the endocervical canal (as see on speculum exam)


Endocervix
  • Endocervical canal
  • Extends from the:
    • Internal os (proximal)
    • External os (distal)

The Normal Cervix:

Histology

  • Exocervix
    • Stratified squamous epithelium
  • Transformation Zone
    • Squamous-columnar junction
    • Metaplastic squamous epithelium
  • Endocervical canal
    • Single layer mucin-producing columnar cells

Exocervix

  • Original squamous epithelium
  • Stratified squamous epithelium
    • Estrogen responsive
    • Usually contains glycogen
    • Basis of Lugol's examination
  • Fine reticular vascular plexus

Original squamous epithelium

  • Proximal extent
    • Original squamous-columnar junction of cervix
  • Distal extent
    • Hart's line
    • Vulvo-vaginal junction
    • Junction between

+ glycogenated squamous epithelium of vagina

+ non-glycogenated squamous epithelium of vulva


Endocervical Canal

  • Columnar epithelium
  • Arranged in longitudinal folds or clefts
    • Extent to depth of 5-8 mm
  • Not true glands
  • Single layer of mucin producing columnar cells
  • Occasional ciliated cells

Original squamocolumnar junction

Line of demarcation between original squamous epithelium and original columnar epithelium


Squamocolumnar junction

  • Changes location over lifetime of woman
  • Estrogen dependent alteration in bulk of cervical stroma
  • Squamous metaplasia
  • Leads to development of the cervical transformation zone

Cervical Transformation Zone

Original squamocolumnar junction

Squamous metaplasia

Current squamous columnar junction


Squamous metaplasia

  • "Normal" physiologic process
  • Columnar epithelium replaced by squamous epithelium
    • Ingrowth from original SCJ
    • Reserve cell hyperplasia
  • Triggered by exposure to acid environment of vagina
  • Mature squamous metaplasia
    • Glycogenated
  • Immature
    • Non-glycogenated
    • Hypothesized to be especially vulnerable to oncogenic HPV


The Normal Cervix
  • Mary M. Rubin RNC, Ph.D., CRNP

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Bibliography

Majority of Cervical Cancers and Precursor Lesions Arise In Immature Squamous Metaplasia of the Cervical Transformation Zone