Hello!
This is Dr. Kingston and
I'm here to discuss the boundaries,
subdivisions, and contents of the oral cavity.
The objective for this video is simply
to describe exactly what the title says.
What are the boundaries, subdivisions,
and contents of the oral cavity?
The oral cavity is bounded superiorly by the palate,
which divides it from the nasal cavity.
Anteriorly, the hard palate is formed by a sheet of bone,
but posteriorly the soft palate provides a sort of
mobile separation with
the nasopharynx that can be opened
and closed as you need it.
The posterior border of the oral cavity
is the palatoglossal arch,
which can be traced inferiorly from the soft palate.
This arch is created by
a fold of mucosa over the palatoglossus muscle,
which elevates the tongue
as we're going to learn in a later video.
This posterior border is what
you might call an incomplete boundary.
So as you can see if you look in the image there,
there's a clear passageway into
the fauces, or the throat, where the palatine tonsils sit.
The lateral and anterior boundaries of
the oral cavity are formed by the cheeks and the lips.
Both of these create pliant walls
that you can change in size
and shape as you flex or
relax different muscles of facial expression.
And inferiorly,
the oral cavity floor is formed by the mylohyoid muscle,
which originates from the mandibular body
at the mylohyoid line and joins
right and left sides in the midline to form a sort
of hammock that supports the oral cavity.
Within the oral cavity,
we divide the area external
from the occlusal plane of the teeth
- so this plane formed here when
the superior and inferior teeth
meet - from the area that's internal to that.
Internal to the occlusal plane is
considered to be the oral cavity proper,
and external is the oral vestibule.
Within the oral vestibule is where we're going to find
the anterior and buccal
surfaces of the teeth and gingivae.
There are several prominent folds of
fibro elastic connective tissue covered by
mucosa that connect the gingivae
out to the lips and cheeks,
as you can see on the image on the left.
The two that anchor the gingivae to
the lips are called the labial frenula
and there's one for each of
the maxillary and mandibular gingivae.
These are embryological remnants
and they can actually be quite
variable in size and prominence from person to person.
Occasionally they end up being so large
that a person has what's considered to
be a lip tie that limits
the mobility of their lips and on those occasions,
they can be surgically reduced.
The oral vestibule is also a site for saliva secretion.
So not only are there
many minor salivary glands
within the mucosa that lines the lips,
the cheeks, the gingivae,
we can also find the opening here of
the parotid duct lateral to the second maxillary molar.
This opening is surrounded by a small papilla,
which is palpable both on
yourself and on your future patients.
Moving on to the lingual side of the teeth,
then, we end up in the oral cavity proper,
and we find that this space is very
much dominated by the body of the tongue.
It's far and away
the biggest thing in there,
and I can pretty much guarantee
you that you're now going to be
exactly aware of how big your own tongue
is for at least the next five minutes.
The tongue is tethered to
the floor of the oral cavity by a band of
fibro elastic connective tissue
called the lingual frenulum.
So just like the labial frenulum,
this is an embryo- logical remnant and
very variable between individuals.
You might have heard the term "tongue tied" before
referring to someone who's
having trouble speaking clearly,
but the term actually refers to a condition called
ankyloglossia, where the lingual frenulum is very robust
and it extends very far
anterior along the floor of the oral cavity,
literally tying the tongue down.
It's not a dangerous condition,
but it can cause trouble with speech and
especially trouble with infant feeding,
so it's usually surgically trimmed back.
We saw the opening of the parotid duct
in the oral vestibule,
and now we're going to see the openings of
our other large salivary glands
in the oral cavity proper.
So on either side of
the lingual frenulum here are sublingual caruncles,
which is a fun word to say.
These are little mounds of tissue that
the submandibular ducts open
through. The submandibular gland-
remember it's down mostly
in the submandibular triangle,
but it has that little thumb piece that sneaks up
underneath the mandible and sends out
its duct anteriorly immediately,
where it will open through these caruncles.
Lateral to the caruncles,
you can follow the sublingual
folds out laterally to the teeth.
These folds are covering up the sublingual glands,
and these are home to many small salivary openings.
The sublingual glands aren't like
the parotid gland or the submandibular gland that have
one big duct that exits
and empties their secretions into the oral cavity.
The sublingual glands have many small ducts,
and these are going to open up
directly onto the oral floor here.
The last space that I'll mention here,
because it's technically part of the oral cavity,
is the sublingual space.
This sits between the mucosa that
covers the oral floor and the mylohyoid muscle.
This is where you'll find the body of
the sublingual gland, the submandibular duct,
and all of the neurovasculature that's
supplying the tongue. There's
enough going on anatomically in this region
that we've chosen to give it its own
learning objective and its own video.
So we'll cover it in more detail there,
but know that this is considered part of the oral cavity.
All right, that is going to bring us to the end of
the content here into your review question.
Please take a few minutes to answer
the question thoroughly and
then I'll walk you through the answer.
The answer is D, the parotid papilla.
It can be palpated in the oral vestibule
immediately lateral to the second maxillary molar.
That is going to bring us to the end of this video.
Thanks for watching.