can detect whether any cancerous cells are
amongst those exfoliated cells. The vagina
is a muscular tube. It’s supported by a lot
of connective tissues to give its strength.
It’s lined by a stratified squamous epithelium.
And that stratified squamous epithelium is
very important for, as I mentioned earlier,
being the wear and tear organ that it is.
Have a look at the right-hand side, and you
can see the epithelial surface, stratified
squamous. You can see at the very base of the
layer of the epithelium sitting on a fairly
tough fibromuscular connective tissue. The
very dark purple lined cells you see there
are going to be cells dividing constantly
to replace cells above them as these cells
are lost or desquamated from the surface,
which is a natural continual process in the
vagina. Notice also that the surface cells,
or at least cells as they move away from the
basal level even, acquire this very pale or
clear stained area. That’s because these
cells start to acquire lots of glycogen in
their cytoplasm. And the glycogen is leaked
out during processing, so you don’t see it
in sections. That glycogen is very important
because it’s secreted or it’s desquamated
into the lumen of the vagina when the cells
are lost. And that glycogen is acted on by
bacteria to produce lactic acid and other
acid types to maintain the environment of
the vagina acidic. And of course, that’s
a barrier to invading pathogens and bacteria.
It’s also a barrier to the sperm. So we’ll
learn in another lecture that seminal fluid
is alkaline to try and neutralize that acidity
and create an almost neutral environment to
optimize sperm transport. I just want to briefly
explain the external genitalia and the clitoris.
The external genitalia consists of the
labia majora. These are two longitudinal folds.
They represent or they’re homologous to
the scrotum in the male, and they contain
smooth muscle that’s homologous to the ductus
muscle in the scrotum of the male. And they
have essentially got hair on one surface and
a smooth non-hairy on the other surface. The
hair on the surface like the scrotum is
pubic hair. And there are also sweat glands and also
sebaceous glands on both surfaces. The labia
minora are also two folds. They represent
or they’re homologous to the skin of the
penis. They’re non-hairy. There’s no hair
on these surfaces, but they too also contain
sweat glands and sebaceous glands. The clitoris
is homologous to the male penis. It has two
cylinders of erectile tissue called the corpora
cavernosa. They are the erectile tissue in
the clitoris. And also there is a gland clitoris
which contains, again, erectile tissue.
It’s not shown in this section, but it contains
erectile tissue and has an enormous number
of sensory nerve fibers. Notice that unlike the
penis, the urethra is not in the erectile tissue.
The mammary gland is a modified apocrine
sweat gland. In fact, it really is a number