So next I'd like to move onto the cervix, so what we're looking at here, is the cervix
bulging into the end of the vagina.
So the portion of the cervix projecting into the vagina is known as the ectocervix, and
I've outlined this in blue.
And then you've got the bit which lines the canal, which lies inside the cervix.
So this is the endocervical canal.
So you've got the ectocervix and the endocervix.
So the endocervix is lined with columnar epithelium, whereas the ectocervix, which is continuous
with the vagina, is lined with squamous epithelium.
So where the columnar epithelium meets the squamous epithelium, is called the squamocolumnar
junction.
So during pregnancy and during puberty, you get eversion of the cervix, so you get the
pushing out of these columnar cells, which line the endocervix and as a result they're
then exposed to the acidic environment of the vagina.
So what happens when the columnar epithelium are exposed to this acidic environment, is
that you get metaplasia, which is a changing of the cell type from columnar to squamous
epithelium.
And this area of change from columnar to squamous is called the transformation zone, and this
zone is important because at this area, the cervix is susceptible to neoplastic change
and ultimately, to possibility of cervical carcinoma, so a common benign condition to
be aware of is a cervical ectropion, which is also called a cervical erosion, so like
I just mentioned, during puberty and during pregnancy, the cervix protrudes out and you
get exposure of the columnar cells to the vagina.
So on speculum examination, you can see the ectropion, or erosion, around the cervical
os, and it's visible as a sort of reddish area, so this is a normal finding in younger
women, pregnant women, and those women who are use the pill.
And it often presents with post-coital bleeding, so that's bleeding after intercourse.
So two other important conditions to talk about are the premalignant, preinvasive stage
of cervical cancer, which is called "cervical intraepithelial neoplasia", and the other
is malignant carcinoma of the cervix.
So on the left here I've draw a very quick diagram of a layer of epithelial cells, sitting
upon the basement membrane.
So invasive cancer is cancer that has spread through the basement membrane.
So cervical intraepithelial neoplasia, or CIN, is this preinvasive stage of cervical
cancer, so it hasn't yet gone through the basement membrane.
So in this premalignant condition, you've got atypical cells, you've got dysplastic
cells and the way that it's detected is often with a smear test.
So a smear test is a cytological test, where cells are sampled from this transformation
zone of the cervix, which is the most common origin, or location for cells to undergo this
dysplastic change.
So it's important to note that the smear is a cytological test, it detects cellular changes
rather than histological changes, but the degree of dyskaryosis, which is the degree
of cellular change, actually reflects the severity of the CIN, the cervical intraepithelial
neoplasia.
And these cellular changes are changes in the nuclear size and also changes in the rate
of mitotic division.
So essentially, it's a histological diagnosis, but the cellular changes do correspond to
what is actually seen on histology.
So there are three grades of CIN, so in grade 1, you've got mild dysplasia, and this affects
the lower third of the epithelium.
In CIN 2, you've got moderate dysplasia, which affects the lower two thirds, of the epithelium,
and in CIN 3, you've got full thickness involvement of the epithelium.
So this is called carcinoma in situ.
So at this stage, if the abnormal cells invade through the basement membrane, you have cervical
cancer.
So in cervical carcinoma, it most often occurs near the external os, at the transformation
zone, and one of the most common causes is the human papillomavirus - HPV, and 90 percent
of the time, cervical carcinoma is of the squamous type, so it's squamous cell carcinoma,
or SCC.
And the second most common type is adenocarcinoma, which involves cells of glandular origin.
So those are some important conditions to be aware of in relation to the cervix.