First of all, this is
the section of the lip. It's taken through
the lower lip as if the person is facing
the left hand of the screen. On the middle
of the lip is a very important muscle,
the orbicularis oris that helps to move
our lips to change the shape of our lips,
and to help in speech, and also a part of the
chewing mechanism and out in the mouth for food.
On the oral side of the lip, you can touch
it with your finger. It's moist.
That's called the oral mucosa. And on the
other surface that you can rub here is
the skin surface. So it's important now that
you orientate where you are looking at on
this section through the lip. There's a border
where the oral mucosa passes over
and then blends on the exterior parts of
the lip on the skin. And that transition
zone is called the vermillion border. That's the
part of the lip that you put lipstick on. In the
central part of the lip labelled here, it's
a bluey clear color, they're labial glands,
tiny little salivary glands. You have them
all throughout the oral cavity. And if
you rung your tongue along the inside of your
lip, you can feel little bumps, they are
these labial glands or very small salivary
glands that help moisten the oral cavity.
You don't see those on the surface of the
lip, up near the vermillion border where
you put your lipstick. So you have to
continually lick your lips to
keep that surface moist.
There are no glands there. What I'd like you to do now
is concentrate on the oral mucosa labelled there.
What stains there, the dark-purple color,
is the epithelium. It's a stratified
squamous epithelium, the sort of epithelium
that's specialized to resist
abrasion and wear and tear, which is ideal
for the oral cavity. It's ideal as
being the oral mucosa. It actually adheres
very tightly to the underlying
lamina propria, which in this case, is not
very loose connective tissue. It's rather
dense collagenous connective tissue. To make
sure that oral mucosa is very
strong during the chewing process and to
resist the abrasion from food moving
about inside the oral cavity.
It's a lot thicker, as you can see, than the skin
on the exterior surface of the lip. If you look
at the skin on the exterior surface of the lip,
you will find there are hair
follicles there, sebaceous glands and sweat
glands. You don't have those of course in
the oral mucosa.