Gross: 8:00 - 9:00Scribe: Laura Adams

Thursday, March 19, 2009Proof: Brittney Wise

Dr. TubbsThe Oral CavityPage1 of 6

The Oral Cavity [S1]:
Let’s start with a simple definition. People call it the mouth, which is a very simplistic way to think about it.
Vestibule vs Oral Cavity Proper [S2]:
The oral cavity can be divided into the oral cavity proper, which is everything that is internal to your teeth, and a vestibule which is every thing between the teeth and the lips/gums.
[S3]
This is an axial cut. As we progress we will learn the borders of the oral cavity. You’ll see that naturally the tongue takes up most of the contents of the oral cavity. Without the tongue it would be a much more captious region.
Teeth [S4]
The teeth are 32 in the adult, less in the non-adult. Before the permanent teeth, there are 20 milk teeth/deciduous/baby teeth.
In the adult, however if you look at the maxillary (top) and mandibular teeth, you will find that you have Medial and lateral incisors. These are copied from top to bottom. You have a canine, a sharp pointed tooth. And you have 2 premolars and 3 molars.
Picture of deciduous teeth [S5]
This shows you a section illustrating some of your deciduous teeth. The permanent teeth are below and haven’t erupted yet.
Tooth Innervation [S6]
For the mandibular teeth all of them receive innervations via the inferior alveolar and a little literature states after anesthetizingthe inferior alveolar some sensation remains in the mandibular teeth. It is thought in these cases that some sensation may come from the nerve to the mylohyoid.
For the superior teeth, (the teeth in the upper jaw bone or the maxillary teeth), are innervated by the superior alveolar nerves (anterior, middle, posterior). The anterior and middle come off the infraorbital and the posterior arises before the nerve becomes the infraorbital so it comes from V2 or the maxillary nerve.
[S7]
Quick clinical picture: this shows that anesthesia of all the lower teeth, on one side anyway, can be accomplished by knocking out the nerve supply at the inferior alveolar nerve. This is done by palpating the lingula and just beside that you will find the entrance into the mandibular canal and the inferior alveolar nerve.
The gingiva [S8]
The soft mucosa lining that is continuous with the mucosal lining of the cheek this is a coronal section. So you should see buccinator muscle and the tongue in cross section. The gingiva helps solidify the connection between the tooth and the bone that it is associated with, mandible in this case. It runs around the tooth and done the lingual surface.
There is a difference in the innervations of the so called buccal side of the gingival verses the lingual side for top and bottom teeth.
Gingival innervations [S9]
Maxillary buccal (in the vestibule) = superior alveolars / infraorbital
Maxillary lingualsurface that is internal to the teeth is greater palatine and nasopalatine especially anteriorly.
Mandibular buccal (external to the teeth) is from buccal branch of V3 (the long buccal nerve) and the mental nerve which is one of the terminal branches of the inferior alveolar nerve.
Mandibular lingual surface (internal to the teeth)is all from the lingual nerve of V3.
Oral Cavity Roof: Hard/Soft Palate [S10]
Now we will look at some of the boundaries of the oral cavity. The roof, which if we remove the mucoperiosteum, we see the boney structures. This picture shows the maxillary teeth.
We have the hard palate, which is know is composed mostly maxillary bone and the horizontal segment of the palatine bone. You will see various suturessuch as the intermaxillary suture, and it is along this suture that you have palatoscesis or split palate that you will have disjunction or disarticulation between those 2 palatal shelves.
In the palatine bone you’ll see the greater and lesser palatine foramens, for the respective neurovascular structures (greater and lesser palatine nerves, veins, and arteries). You also have incisive foramen.
Posterior nasal spine, remember from Salter’s lecture, that is the main attachment for the muscle inside the uvula, the midline structure from the soft palate posteriorly.
Diagram of the muscles [S11]
If we look at the junction between the soft and the hard palate, we have removed the mucoperiosteum. The soft palate attaches along the posterior edge of the palatine bone.
The 2 prominent muscles of the soft palate are the tensor veli palatine (coming around the hamulus) and the levator veli palatine. Other muscles associated with the soft palate are the uvularis (musculi uvuli). Notice the relationship of the tensor veli palatine and the levator veli palatine to the eustachian tube.

Gag Reflex [S5]
Here is a picture of the uvula in vivo.
The posterior portion of the oral cavity or the oropharynx. In any routine exam you look for the position of the uvula. You want the uvula to keep a midline position, when you ask the patient to phonate (speak). You can see some associations of that uvula with the soft palate for example if we follow the soft palate over we see the palatopharyngeal arch and palatoglossal arch, which is more anteriorly located. And in between these 2 arches is the palatine tonsil. In this person, most likely older, is is somewhat atrophied. To see this you really have to depress the tongue.
The gag reflex is an important reflex in keeping things out of the oropharynx that don’t belong there. For example, the uvula and associated soft tissues of the soft palate are extremely sensitive to touch, some people more than others. If you put a finger or tongue depressor back there it illicits a gag reflex.
This reflex simply has a sensory limb from the glosspharyngeal nerve and a motor limb that contracts those pharyngeal muscles from the vagus nerve and specifically its pharyngeal branches. So when you test someone’s gag reflex you are testing both their IX and X cranial nerves.
[S13]
Now if somebody has a problem with their X cranial nerve or especially its source from the brainstem (nucleus ambiguous) you will see something of this sort. So if the right vagus nerve of pharyngeal plexus is disrupted, you’ll see that the right side of the soft palate is a little more inferiorly located and the tip of the uvula with such a gag reflex will point to the contralateral side (away from the side of the lesion).
Hard/soft palate Sensory/Motor Innervation[S14]
The muscles of the soft palate are innervated form the pharyngeal branch of X. With the exception of the tensor veli palatine which gets its innervations from V3. Sensory and autonomic are carried in the greater and lesser palatine nerves. Remember the greater travels anteriorly and the lesser travel posteriorly covering the soft palate. If you burn the roof of your mouth, you’re stimulating the greater palatine nerve most likely.
Oral Cavity Floor [S15]
If you press on the submandibular region and push up, you actually pressing the mylohyoid muscle (thin muscle) and just beyond that is the tongue. So there is not a lot of tissue between the external surface and the mylohyoid. So if the mylohyoid is deinnervated from an injury and you depress the tongue, you can see a bulge coming out of the submandibular region which is just the tongue coming down.
Oral Cavity Floor[S16]
So there’s the mylohyoid reflected and we have another smaller, closer to the midline muscle called the geniohyoid. It attaches to the mandible from the genial spines (superior and inferior) and it specifically arises from the inferior genial spine.
Genial refers to the mental region.
[S17]
Now this is a beautiful internal view of that same floor. Most of the tongue has been removed. We are looking from the inside out toward the mandibular teeth (or what’s left of them.) We see the geniohyoid muscle.
This is the genioglossus, which is an extrinsic tongue muscle. The tongue is basically a grouping of several skeletal muscles. They have several different attachments one coming from the mandible, the genioglossus.
We have cut the tongue out and we see the mylohyoid that extends from molars to the molars on the other side (that is what “mylo” is referring to.) The geniohyoid is more in the midline. This muscle was mentioned when we learned the suprahyoid muscles, and the geniohyoid receives its innervations from C1 fibers which hitchhiked along with XII to get there.
If you canget this slide in your mind it really helps you with orientation in the lab. The following are other features he said to study on your own: Glossoepiglottic folds, Lingual artery, Facial artery, Digastrics, Stylohyoid, and Middle constrictor
[S18]
This shows the floor again. This is sometimes referred to as the oral diaphragm. So we have thoraco-abdomial diagram, aperitoneal diagram, and oral diagram to name a few.
Geniohyoid in the midline, and the mylohyoid.
We also see our smaller salivary glands, the sublingual gland and our submandibular gland (which remember has a superficial and deep component.)
[S19]
Here is a Germanic view of the geniohyoid muscle. “Germanic” because it was copied from an older German atlas.
SQ: what has been cut off at the top near the incisors?
Answer: the genioglossus, the genio-tubercles in the front (superior and inferior) give rise to the genioglossus, the superiors and inferiors, and the geniohyoid. So if you cut the tongue out by necessity you cut through the genioglossus.
Oral Cavity Lateral Wall [S20]
If we exclude the mucosa, and any fascia that may be lateral to this muscle – the buccinator. We have seen this in the face, but you may be able to see it from the internal perspective. Posteriorly, the buccinator has an attachment into the pterygomandibular raphe, a connective tissue line, and the muscle that is continuous with that posteriorly is the superior pharyngeal constrictor.
[S21]
Buccinator muscle is a muscle of facial expression, although it doesn’t give you much expression. Some people include it as an accessory masticating muscle although it is not innervated by the trigeminal nerve. The accessory masticatory component is that when this muscle becomes tense, it aligns food so that it maintains the food between the molars. It you lose this tensity in the buccinator you might complain that you food ends up in the vestibule when you are trying to chew.
Posterior Border: Fauces [S22]
We see the opening into the oropharynx and what is called the fauces, which literally means throat. From this perspective as I showed you earlier, we see the uvula, the 2 tonsilar pillars (palatoglossal and the palatopharyngeal folds and their associated muscles.)
So as you go from the oral cavity and start to move posteriorly you’ll move into the oropharynx.
Anterior border: Lips[S23]
Anteriorly, we have the lips. This is a sagittal section. We see the mandible, tongue and lip. It is comes of the mucosal lining (the skin) and the skeletal muscle. They function in grasping, sucking, speech, and osculation (kissing).
Sensory innervations are from the superior labial from infraorbital nerve to the upper lip, and the inferior labial from mental nerve to the lower lip. Inferior alveolar nerve block causes the skin of the lower lip to be numb.
Philtrum [S24]
The midline furrow below the nose above the lip. It means “to love”. The Greeks thought this was a very erogenous part of the body.
In more modern times, so in 15/16th century Europe where people didn’t bath, people began to smell other people or themselves. They would place perfume on the philtrum to block out the bad smell.
Salivary Glands [S25]
We talked about the parotid gland. We saw that it has to take the saliva they make and drain it into the oral cavity via a duct. So each gland has a duct associated with it. The parotid gland is in the paraotic region. The sublingual and submandibular glands we see in the oral cavity, the sublingual gland entirely and submandibular partially (the superficial, larger portion resides at the edge of the mandible. If you stimulate it you will feel saliva pooling in your mouth.)
[S26]
These glands may seem small but they can produce up to a 1 pint/day. Some people have trouble with their lower lips because of a injury from a stroke or cerebral palsy. If you don’t have the lower lip then you tend to droll saliva from the oral cavity.
One treatment for these patients is to remove some of the salivary glands. Now the parotid gland is difficult because of the facial nerve, the lingual gland is hard to get to, but the submandibular gland is easy to get to (the majority of it is superficial). You will often see an incision below the mandible on stroke and CP patients, where a large part of the submandibular gland has been removed.
Innervation is fairly straight forward. The glosspharyngeal nerve innervates the parotid gland via the otic ganglia. The submandibular and sublingual glands are innervated by the facial nerve to the submandibular ganglia.
7th nerve palsy, or bell’s palsy, would cause dry mouth.
[S27]
Remember that the termination of these ducts are into the oral cavity.
Stenson’s duct, or parotid duct, was by the 2nd upper molar. That site is also a common location for a stone that develops in the salivary tubes. Patients may present with swelling around the ear and you may find that they simply have a little stone that is lodged in the opening of the parotid duct. This causes the saliva to build up into the parotid gland. Remove the stone and the swelling goes away.
[S28]
The opening of the submandibular duct and the sublingual ducts are right below the front of the tongue.
Submandibular duct openings are on the sides of the frenulum, which is the midline tether.
So people are born with frenulum that is too taut, this is causes tongue-tied or ankyloglossus. So simply cut this frenum to allow proper movement.

[S29]
We will go on and look at a very nice view of the sublingual and submandibular glands. We notice this C-shaped submandibular gland. The superficial part we saw earlier when we did the suprahyoid region and then the “tail” region that courses superior and on top of the mylohyoid muscle.
The submandibular duct proceeds anteriorly to open on either side of the frenulum.
The sublingual glands sit entirely superficial, or superior to the mylohyoid. Some of its drainage may be into the submandibular duct and it has little individual ductlets that may drain directly into the oral cavity.
Another name for the submandibular duct is the duct of Wharton and another name for the accessory ducts from the sublingual is _____? [Inaudible]
Look at the relationship between the lingual nerve and the submandibular duct which proceeds from a posterior to anterior direction. Lingual nerve will come down into the oral cavity from V3 and will cross that submandibular duct on its lateral service and also on its medial surface. As it enters the oral cavity just at the edge of the mylohyoid, look at the relationship between the nerve and the third molar.
A third molar extraction can cause injury to the lingual nerve because of an intimate relationship between the roots and the nerve. This can cause lose of touch and taste in the anterior 2/3 of the tongue because the corda tympani has already become involved with this nerve.
[S30]
This is a older picture but it shows you the little accessory sublingual ducts stringing directly into the oral cavity.
It shows you a nice relationships between the lingual nerve, how it crosses the submandibular duct (on the lateral and medial surface) and look at the opening of Stenson’s duct (parotid duct) just adjacent to the 2ndmaxillary molar.
Accessory Salivary Glands [S31]
In addition to the 3 major glands, you have a lot of accessory glands, located in the palate, lips, cheeks, around the tonsils, and around the tongue. If we de-glove the face, take off the muscles of facial expression, you would see a smattering of accessory salivary glands.
[S32]
This shows you a nice collection of palatal salivary glands, in the hard and soft palate.
Submandibular ganglion [S33]
You can find this in your cadaver. It is suspended from the lingual nerve. It is not functionally associated with the lingual gland, just structurally located with it. So preganglionic fibers of the corda tympani that are traveling with it will come off and synapse into this ganglion and then their postganglionics are destined for the submandibular and sublingual glands.
Look for it, suspended on the inferior surface of the lingual nerve and just superficial to the hyoglossus muscles, one of the extrinsic tongue muscles.
Extrinsic tongue (L.