Anatomy of the oral cavity

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Introduction0:00–0:59

When you’re eating a slice of pizza, the first place food enters is the oral cavity and it is actually where digestion starts.
Here, we get to taste the pizza and form a bolus of food to swallow for further digestion in the gut. Many structures work together to chew and swallow like the lips, teeth, and palate, so let’s explore them!Now, the oral cavity itself is divided into the oral vestibule and the oral cavity proper.
The vestibule is the compartment between the anterior and lateral aspects of the teeth and gingiva and the posterior and medial aspects of the lips and cheeks.
Moving further inside is the oral cavity proper, bounded by the dental arches anteriorly and laterally, and the palate superiorly.
The oral cavity proper is mainly occupied by the tongue.Now let’s get back to that slice of pizza. To eat it, first you open your mouth, and the opening through which the food enters is called the oral fissure.

Lips0:59–3:11

Once the pizza’s inside the oral cavity, you use the lips, which act like valves, to keep the oral fissure closed and the food inside while you’re chewing.
The lips, and the muscles within it, also help us exhale through the mouth, whistle, speak, or kiss. Now, the lips extend from the nasolabial sulci and the nares to the mentolabial sulcus, which is just inferior to the lips, but not all of its surface looks the same.
The most remarkable feature is the part we’re actually used to calling “lips”: a thin, hairless, reddish skin, called the transitional zone, because it represents the transition between the skin of the face and the inner labial mucosa.
The vermillion border is the outer edge of our lips that marks the limit between the skin of the face and the transitional zone.
Finally, in the upper lip, is the philtrum which is a groove superior to the lips that extends from the midline of the vermilion border to the nasal septum.Now, the lips get their blood supply mainly from branches of the external carotid arteries.
Specifically, the facial artery gives the superior and inferior labial arteries which anastomose with one another in the midline.
Innervation is provided by the trigeminal nerve, specifically through the maxillary nerve or Cranial Nerve V2 and the mandibular nerve or Cranial Nerve V3.
The maxillary nerve branches into the infr aorbital nerve, which gives off superior labial branches for the upper lip. The mandibular nerve branches into the mental nerve, which gives off inferior labial branches that supply the lower lip.Finally, the lips’ lymphatic drainage goes to the submental lymph nodes for the medial part of the lower lip; and to the submandibular lymph nodes for the upper lip and the lateral parts of the lower lip.Next up, are the gingivae, or gums, which are continuous with the inner side of the lips.

Gingivae3:11–3:49

They’re made up of connective tissue covered by mucosa, and they cover part of the teeth and the alveolar processes of the maxillary and mandibular bones.
There are two types of gingiva: immediately next to the labial mucosa is the unattached gingiva, or alveolar mucosa, which is red, shiny and loose; and surrounding the teeth and alveolar processes is the attached gingiva, or gingiva proper, which is more pale and tightly attached to the subjacent bone.Alright now, back to that slice of pizza.

Teeth3:49–10:14

Once it is inside the mouth, the next step is to take a bite and start chewing. This is where the teeth come into play.Now, besides cutting and chewing food, teeth are also important during speech, since there’s certain letters or phonetic sounds that are pronounced by pressing the tongue against the teeth, like the “T” sound for example.
Now, we don’t have only one set of teeth for all our life, we actually have two of them. The first set of 20 teeth we grow during the first years of childhood are called the primary, or deciduous teeth, since they eventually fall out.
And the second set of 32 teeth we have as adults, are the secondary, or permanent teeth.So, all these teeth help us turn that delicious pizza into a bolus of food.
But not all of our teeth have the same features and functions. On each side of an adult’s set of teeth there are: two incisor teeth, right next to the midline, which you would use to cut the pizza; one canine, used to tear the food; and two premolars and three molars, that you’d use to grind the food as you chew.
Each of these teeth is made of three parts: the crown, the root, and the neck. The crown is the part we see when people smile, the root is nailed within the tooth socket of the alveolar processes, and the neck is a small part between the crown and the root, covered with gingivae.
Now, the teeth are actually living tissue, so they need to be nourished and innervated just like any other anatomical structure.
So, inside each tooth, there is a pulp cavity, which houses the blood vessels and nerves, as well as connective tissue between them to fill the cavity.
At the tip of the root, there’s an opening, through which the vessels and nerves enter or exit the pulp cavity, called the apical foramen.
Now, surrounding the pulp cavity, the hard structure of the teeth is mostly made up of dentin, which is all over the crown, neck, and root.
In the crown, the outer surface of the dentin is coated with enamel, which is what we actually see; and in the root, dentin is coated with cementum.Cementum also works as the surface of articulation of the teeth with the tooth sockets, which are the individual cavities found in the alveolar processes of the maxilla and mandible.
Since they’re basically bony structures, the tooth sockets are covered with periosteum. Now, between the periosteum of the tooth socket and the cement of each tooth, there’s a tissue called the periodontium, or periodontal membrane, made mainly of collagen fibers.
The periodontium works like a ligament between the articular surfaces and makes this a very particular type of joint, unique in the human body, called a dento-alveolar syndesmosis, or gomphosis, where “gomphos-” means peg, referring to the way teeth are fastened into the tooth sockets.Okay, now, both the teeth and gingiva get their arterial blood supply through branches of the maxillary arteries.
The lower teeth and the corresponding gingiva facing the lips, called buccal gingiva, are supplied by inferior alveolar artery branches, directly from the maxillary artery.
The upper teeth and their corresponding buccal gingiva are supplied by the posterior and anterior superior alveolar arteries.
The posterior branch arises directly from the maxillary artery and supplies the molar and premolar teeth. The anterior branch originates from the infraorbital artery branch of the maxillary artery, and supplies the canine and incisor teeth.Venous drainage is through the inferior alveolar vein for the lower teeth and gingiva, and the anterior and posterior superior alveolar veins for the upper teeth and gingiva.
They follow the same paths as the arteries but drain into the pterygoid plexus of veins, ultimately draining into the internal jugular vein.
Some veins from the lower teeth may also drain into the facial vein.The gingiva facing the tongue, called lingual gingiva, is supplied by branches of the lingual artery; and the one facing the palate, called palatal gingiva, is supplied by branches of the sphenopalatine and greater palatine arteries.
Veins also follow the arteries and end up draining into the facial vein or the pterygoid plexus.Finally, lymph from the teeth and gingiva drain into the submandibular, submental, and deep cervical lymph nodes.Now let’s look at the nerves that supply the teeth and gingiva, which are all branches of the trigeminal nerve or CN V.
The upper teeth and gingiva are innervated by branches of the maxillary nerve or CN V2.In the pterygopalatine fossa, this nerve branches into the posterior superior alveolar nerve.
Then, in the orbit, another branch of the maxillary nerve, called the infraorbital nerve, gives the middle and anterior superior alveolar nerves.
These three superior alveolar nerves innervate the upper teeth and the buccal gingiva. The palatal gingiva is innervated by another two branches of the maxillary nerve: the greater palatine and the nasopalatine nerves.Now, the lower teeth and gingiva are innervated by branches of the mandibular nerve or Cranial Nerve V3.
In the infratemporal fossa, this nerve branches into the inferior alveolar nerve, which innervates the lower teeth. The buccal gingiva is innervated by a branch of the inferior alveolar nerve called the mental nerve, and a branch of the mandibular nerve called the buccal nerve.
Finally, the lingual gingiva is innervated by the lingual nerve.Alright now, before we move on, let’s take a quick pause to see if you can label the types of teeth labeled A, B, C and D, and their different parts from 1 to 3 in the following images.Great!

Quiz10:14–10:33

Palate10:33–13:04

Now let’s switch gears and look at the palate, which makes up both the roof of the mouth and the floor of the nasal cavity.
It’s made up of the hard and the soft palate, both lined with oral mucosa on their inferior surface. This mucosa is tightly packed with palatine glands, which secrete mucus.
The hard palate, made up of bone, is the anterior two thirds (⅔) of the palate and the posterior third is the soft palate, made of aponeurosis anteriorly and muscles posteriorly.
From the posterior border of the soft palate hangs the uvula.Alright now, at the posterior end of the oral cavity there’s an area called the fauces or isthmus of the fauces, which is a passage between the oral cavity and the oropharynx.
The fauces are bounded by the soft palate superiorly, the tongue inferiorly, the palatoglossal arches anteriorly and the palatopharyngeal arches posteriorly.
As their names suggest, the palatoglossal arches extend from the soft palate to the tongue, and the palatopharyngeal arches from the soft palate to the pharynx.
Between them, there’s a space called the tonsillar bed; where the palatine tonsils are found, which are made of lymphoid tissue, so they’re part of the immune system.
The main artery that supplies the tonsils is a branch of the facial artery called the tonsillar artery. The ascending and descending palatine, lingual, and ascending pharyngeal arteries also help supply the tonsil.Let’s take a closer look at the hard palate now.
The bones that form the hard palate are the palatine processes of the maxillary bones anteriorly and the horizontal plates of both palatine bones posteriorly.
The maxillary teeth border the hard palate anteriorly and laterally. Posterior to the incisor teeth, there’s the incisive fossa, which has one or more incisive foramina, that allow the nasopalatine nerve and the sphenopalatine artery to pass through.
Posteriorly and laterally, on the horizontal plate of each palatine bone, is the greater palatine foramen; and the lesser palatine, foramen through which the greater and lesser palatine arteries and nerves pass.
Alright, that’s a lot of information to take in, so feel free to pause the video and see if you can label the parts of the hard palate labeled from A to E.

Quiz13:04–13:17

Now, the pharynx is like a crossroads for the air, which normally enters and exits through the nose, and the food that enters through the mouth.

Soft palate muscles13:17–16:48

The soft palate acts like a gate that determines which path is taken and this is possible thanks to the muscles within it, and the best part is, the names of these muscles give a bit of information about their actions or insertions.
First up, we’ve got the tensor veli palatini, where “tensor” means “tenses” and “veli palatini” refers to the soft palate, which looks like a veil.
This muscle originates on the scaphoid fossa of the sphenoid bone and the cartilage of the auditory tube. The muscle runs downwards and its tendon passes lateral to the pterygoid hamulus and then runs medially to insert on the palatine aponeurosis.
The tensor veli palatini uses the pterygoid hamulus as a pulley to tense the soft palate. This happens when we yawn and when we swallow, since a tensed soft palate allows the tongue to push against it in order to propel the bolus of food towards the oropharynx.
In addition, this also opens the auditory tube. The mandibular nerve, which is a branch of the trigeminal nerve, innervates this muscle.
Next up, is the levator veli palatini, where “levator” means “elevates” and veli palatini refers to the soft palate. This muscle originates on the petrous part of the temporal bone and the cartilage of the auditory tube.
It runs inferiorly to insert on the palatine aponeurosis, just like the tensor veli palatini, and it elevates the soft palate when we swallow or yawn.
This muscle is innervated by the pharyngeal plexus of the vagus nerve.Now, with the palatoglossus muscle, “palato-” refers to the palate, and “-glossus” to the tongue.
So this muscle originates on the palatine aponeurosis superiorly, and inserts on the side of the tongue inferiorly. Since both attachments are made of soft tissue, when it contracts, the palatoglossus brings these structures together, depressing the palate and elevating the tongue.
This closes the isthmus of the fauces, which aids in the initiation of swallowing and also allows us to breath through the nose even when our mouths are closed.
Innervation of this muscle is also by the pharyngeal plexus of the vagus nerve.Something similar happens with our next muscle, the palatopharyngeus.
It originates on both the hard palate and the palatine aponeurosis and runs posteroinferiorly to insert on the wall of the pharynx, bringing these structures together when it contracts.
Therefore, the palatopharyngeus tenses the soft palate and elevates the pharynx. This muscle is also innervated by the pharyngeal plexus.The musculus uvulae originates on the posterior nasal spine of the hard palate and runs posteroinferiorly to insert on the mucosa of the uvula to shorten it when it contracts.
And yet again, this muscle is innervated by the pharyngeal plexus.Finally, let’s discuss the arterial supply and innervation of the palate, starting with vascularization.

Palate neurovasculature16:48–19:47

All the arteries that supply the palate are branches of the external carotid artery.The external carotid artery gives off two main branches to supply the palate: the maxillary, and the facial arteries.
In the pterygopalatine fossa, the maxillary artery gives off a branch called the descending palatine artery, which runs downward along the sphenopalatine canal and gives two branches: the greater and lesser palatine arteries.
The greater palatine artery enters the oral cavity through the greater palatine foramen, then it runs anteriorly to supply the inferior surface of the hard palate until it passes through the incisive canal to exit the oral cavity and enter the nasal cavityThe lesser palatine artery enters the oral cavity through the lesser palatine foramen and then heads posteriorly to help supply the soft palate.
Now, right after the facial artery branches from the external carotid, it gives off the ascending palatine artery, which runs superiorly on the lateral surface of the superior constrictor muscle of the pharynx.
When the artery reaches the superior border of this muscle, it gives a palatine branch that turns medially and heads towards the soft palate to supply it.The veins that drain the palate follow the arteries that supply it, and end up draining into the pterygoid plexus of veins, just like the veins that drain the teeth and buccal gingivae.
This plexus mainly drains into the maxillary veins, which end up draining into the internal jugular vein.Finally, let's look at the innervation of the palate.
The sensory innervation of the palate is through branches of the maxillary nerve - CNV2. In the pterygopalatine fossa, the maxillary nerve gives off two branches that enter the sphenopalatine ganglion.
Their fibers branch directly from the ganglion to form the greater and lesser palatine nerves, which travel down the sphenopalatine canal and enter the oral cavity through the greater and lesser palatine foramina, respectively, and follow the same paths as the palatine arteries.
The greater palatine nerve innervates most of the hard palate and the lesser palatine innervates the soft palate.Now, the maxillary nerve gives off another branch in the pterygopalatine fossa called the nasopalatine nerve.
This nerve enters the nasal cavity first, through the sphenopalatine foramen. After innervating the septum, the nasopalatine nerve enters the oral cavity through the incisive canal and innervates the anterior part of the hard palate.Now let’s take a quick quiz before the recap!
Can you complete the chart with the actions and innervation of the muscles of the soft palate?Alright, as a quick recap, the oral cavity is divided into the oral vestibule and the oral cavity.

Quiz19:47–19:59

The lips are made up of the transitional zone, the vermillion border, and the philtrum. The lips are supplied by the superior and inferior labial arteries, branches of the facial arteries; and innervated by the superior and inferior labial nerves, branches of the maxillary and mandibular nerves, respectively.

Review19:59–22:49

The gingivae cover part of the teeth and the alveolar processes. The teeth help cut and chew food and are made of three parts: the crown, the root, and the neck.
Inside, there’s the pulp cavity, which houses the blood vessels and nerves that enter through the apical foramen to supply the tooth.
The dentin forms the skeleton of the tooth, and is coated with enamel in the crown, and cementum in the root. Three branches of the maxillary artery supply both the lower and upper teeth: the inferior alveolar, and the posterior and anterior superior alveolar arteries.
The upper teeth and gingiva are innervated by branches of the maxillary nerve and the lower teeth and gingiva by branches of the mandibular nerve.
The palate makes up the roof of the mouth, with the hard palate anteriorly and the soft palate posteriorly. The hard palate is made up of the palatine processes of the maxillary bones and the horizontal plates of both palatine bones.
Within each lateral boundary of the fauces is the tonsillar bed, that houses the tonsils, between the palatoglossal and palatopharyngeal arches.
The muscles of the soft palate are the tensor and levator veli palatini, the palatoglossus, the palatopharyngeus, and the musculus uvulae.
The tensor veli palatini is innervated by the mandibular nerve, and the rest are innervated by the pharyngeal plexus of the vagus nerve.
The arterial supply of the palate is supplied by the greater and lesser palatine arteries for the hard and soft palate, respectively, and the ascending palatine artery, which supplies the soft palate.
The sensory innervation is from the greater and lesser palatine, and the nasopalatine nerve which are branches from the maxillary nerve.
The veins that drain the oral cavity drain into the pterygoid plexus, which mainly drains into the internal jugular vein.
which supplies the soft palate. The sensory innervation is from the greater and lesser Palatine and nasal Palatine nerve which are branches from the maxillary nerve.
The vet said during the oral cavity plexus, which mainly drains into the internal jugular vein.