17. The Cervix Flashcards
How is the uterus anatomically divided?
The uterus is divided into the corpus (body), isthmus, and cervix.
What is the length of the cervix in an adult?
The cervix measures 2.5 to 3 cm in length in the adult.
What is the typical orientation of the cervix?
The cervix is usually angled downwards and backwards.
What is the vaginal portion of the cervix called, and how is it structured?
The vaginal portion of the cervix is called the portio vaginalis or ectocervix. It is divided into anterior and posterior lips, with the external os in the center.
What connects the external os to the uterine cavity?
The external os is connected to the uterine cavity by the endocervical canal (endocervix).
What is the shape and largest diameter of the endocervical canal?
The endocervical canal is an elliptical cavity, measuring 8 mm in its greatest diameter.
What is the blood supply to the cervix?
The cervix is supplied by the descending branches of the uterine arteries.
How does the venous drainage of the cervix occur?
The venous drainage parallels the arterial system and communicates with the cervical venous plexus and the neck of the bladder.
Where do the lymphatics of the cervix drain?
The lymphatics of the cervix drain into two lateral plexuses in the region of the isthmus, which then drain to the external iliac and obturator nodes, the internal iliac nodes, the common iliac nodes, and the sacral nodes.
What types of tissue compose the cervix?
The cervix is composed of fibrous, muscular, and elastic tissue.
What are the two types of epithelium lining the cervix?
The cervix is lined by squamous epithelium and columnar epithelium.
What is the squamocolumnar junction (SCJ) of the cervix?
The SCJ is the border between the stratified squamous epithelium and the mucin-secreting columnar epithelium of the endocervix.
What is the original squamocolumnar junction (OSCJ)?
The OSCJ is the SCJ where the squamous epithelium meets the columnar epithelium at birth.
What is the new or functional squamocolumnar junction?
The new SCJ is formed after metaplasia converts columnar epithelium into squamous epithelium. This is the SCJ typically visualized in adult women.
What is the transformation zone (TZ) of the cervix?
The TZ is the area between the original SCJ and the new SCJ, where metaplasia occurs.
What causes the development of the transformation zone?
The development of the TZ depends on changes in the length and size of the cervix as the female develops and is exposed to estrogen.
What are the two mechanisms by which columnar epithelium is replaced by squamous epithelium?
- Direct ingrowth of original squamous epithelium bordering the columnar epithelium.
- Proliferation of undifferentiated subcolumnar reserve cells of the endocervical epithelium that differentiate into squamous epithelium (squamous metaplasia).
What is metaplasia?
Metaplasia is the physiological conversion of one mature type of epithelium into another equally mature type.
When is metaplasia most active in women?
Metaplasia is most active during reproductive life and is quiescent in pre-menarchal and post-menopausal women.
Why is the transformation zone important?
The transformation zone is important because almost all cervical squamous neoplasias and their precursors originate in this area.
Where is the transformation zone typically located?
In the vast majority of women, the transformation zone is located on the ectocervix.
In what percentage of women is the original squamocolumnar junction located on the vagina?
In around 4% of women, the OSCJ is located on the vagina.
What is the role of cervical cancer screening in cancer prevention?
Cervical cancer screening detects precursors to cervical cancer early, allowing for treatment and follow-up to prevent the development of cancer. This is known as secondary prevention
Which test is used for cervical cancer screening?
Cervical cytology, commonly performed as a Pap smear, is used for cervical cancer screening.
What is the target population for cervical cancer screening in the UK?
Women aged 25 to 60 years are the target population for cervical cancer screening in the UK
How does the incidence of cervical cancer differ between countries with and without screening programmes?
Countries with no organised screening (e.g., sub-Saharan Africa, Latin America): 40–100 cases per 100,000 women.
Countries with high-coverage screening (e.g., the UK): 5–7 cases per 100,000 women.
Countries with poorer coverage and health services (e.g., the Balkans): 20 cases per 100,000 women.
What is the incidence of cervical cancer in the UK with high coverage of screening?
Around 5–7 cases per 100,000 women.
What percentage of the target population is covered by the cervical cancer screening programme in the UK?
The UK screening programme covers 87% of the target population.
What is the cumulative reduction in cervical cancer with yearly screening?
Yearly screening reduces cervical cancer incidence by 93%.
How many Pap smears are performed over a lifetime with yearly screening, and what is the reduction in cervical cancer incidence?
Number of Pap smears: 30.
Cumulative reduction in cervical cancer: 93%.
How does the effectiveness of three-yearly screening compare to yearly screening?
Three-yearly screening reduces cervical cancer incidence by 91%, which is only slightly less than the 93% reduction with yearly screening.
Three-yearly screening requires fewer Pap smears (10 vs. 30).
What is the cumulative reduction in cervical cancer with five-yearly screening
Five-yearly screening reduces cervical cancer incidence by 84%.
How effective is ten-yearly cervical cancer screening?
Ten-yearly screening reduces cervical cancer incidence by 67%.
How does the frequency of screening impact the number of Pap smears required?
Yearly screening: 30 Pap smears.
Three-yearly screening: 10 Pap smears.
Five-yearly screening: 6 Pap smears.
Ten-yearly screening: 3 Pap smears.
Why is cervical cancer more common in countries with no organised screening programmes?
Lack of screening leads to undetected and untreated cervical cancer precursors, resulting in higher cervical cancer incidence.
What is the basis of the South African Cervical Cancer Screening Policy?
Offer asymptomatic women over the age of 30 three free Pap smears in their lifetimes, spaced 10 years apart.
What is the difference between a screening Pap smear and a diagnostic Pap smear
Screening Pap smear: Reserved for asymptomatic women as part of a national secondary prevention programme.
Diagnostic Pap smear: Performed in symptomatic women (e.g., abnormal vaginal bleeding, discharge, or pain) as part of a medical work-up.
Why does the South African policy focus on screening women over the age of 30?
The yield of disease detection is higher in older women.
Cervical cancer precursors have a long latent period (10–20 years) to progress to cervical cancer.
Screening younger women is less cost-effective as their precursors are often transient with high regression rates, except in HIV-positive immuno-incompetent women.
What is the incidence of cervical cancer precursors in HIV-negative and HIV-positive women?
HIV-negative or immuno-competent HIV-positive women: Peak incidence in their early 30s.
HIV-positive immuno-incompetent women: Develop precursors earlier with faster progression to cervical cancer.
How effective is infrequent cervical cancer screening?
Screening every 10 years is associated with a two-thirds reduction in the incidence of cervical cancer.
Why is the detection of cervical cancer precursors in asymptomatic women not considered a medical emergency?
Cervical cancer precursors have a long latent period (10–20 years).
Asymptomatic women with macroscopically normal cervices require follow-up but not urgent intervention.
Why is colposcopy still necessary in asymptomatic women with normal-looking cervices?
Early micro-invasive cancers can develop in a normal-looking cervix.
Colposcopy is performed following specific guidelines to detect such cases.