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Anatomy of the oral cavity (dentistry)

Notes

Transcript

Content Reviewers:

Yifan Xiao, MD

The mouth, or the oral cavity, does a variety of jobs that range from playing the trumpet, or kissing, to more vital roles like chewing and swallowing your favorite food.

It’s the point of entry into the gastrointestinal system but also acts as an alternative respiratory pathway in case your nose gets blocked and helps produce and modify sound when you speak or sing.

Now, the oral cavity is a space that extends from the inner surface of the lips to the beginning of the oropharynx, which is marked by the junction of the hard and soft palate above; the anterior pillars, or the palatoglossal arches, laterally; and the terminal sulcus of the tongue below.

The roof of the oral cavity is formed by the palate, which separates the oral cavity from the nasal cavity above.

At the bottom, the mylohyoid muscle forms a muscular diaphragm that supports the tongue and the structures of the floor of the mouth.

Finally, the lateral walls of the oral cavity are formed by the cheeks.

The oral cavity is divided by the teeth and the inner oral mucosa into two parts; the smaller, oral vestibule, and the larger, oral cavity proper.

The oral vestibule is a small slit-like space between the teeth and inner mucosal lining of the lips and cheeks.

The mucosa of the lips and cheeks continues onto the gingiva to form the superior and inferior boundaries of the vestibule.

The oral cavity proper is the space contained within the upper and lower dental arches.

It extends from the inner surface of the teeth and communicates with the oropharynx posteriorly.

Now, when the mouth is open, the oral vestibule becomes continuous with the oral cavity proper.

However, some amount of communication is maintained even when the jaws are shut.

This is achieved through a tiny space called the retromolar fossa, which lies behind the third molar teeth and the ramus of the mandible.

The basic bony framework of the oral cavity is formed by three main bones; the mandible or the lower Jaw bone, the maxilla or the upper jaw bone, and the palatine bones.

The mandible and maxilla, like most bones in the human body, have a core of less dense cancellous bone, wrapped in an outer layer of more dense, compact bone.

The opposing surfaces of the Maxilla and mandible have a horseshoe-shaped ridge known as the alveolar process.

The alveolar processes contain tooth sockets, or dental alveoli, for the teeth to rest in.

The maxilla also gives rise to palatine processes that are fused together in the midline forming the anterior two-thirds of the hard palate, whereas the posterior one-third of the hard palate is formed by the horizontal plates of the palatine bone.

Now, the roof of the mouth is formed by the palate mouth and separates it from the nasal cavity.

The anterior part is made up of the hard palate, and the soft palate forms the posterior part.

The hard palate is a bony, dome-shaped structure against which the dorsum of the tongue rests while the mouth is closed.

The upper surface forms the floor of the nasal cavity and is lined by the respiratory mucosa.

Whereas the lower surface is covered by the palatal gingiva near the alveolar process, and the masticatory mucosa covers the remaining part.

Next comes the soft palate, which juts out from the back of the hard palate and separates the oropharynx and nasopharynx.

It’s a boneless movable structure made up of a fibrous aponeurosis, muscles, and a thin, nonkeratinized mucosa.

Just like the hard palate, the soft palate is also covered by the oral mucosa inferiorly, and the respiratory mucosa superiorly.

Within the mucosa, the soft palate contains five muscles, which include tensor veli palatini, levator veli palatini, musculus uvulae, palatoglossus, and palatopharyngeus.

The tendon of tensor veli palatini flattens to form a fibrous sheath called the palatine aponeurosis.

The lower edge of the soft palate suspends a small grape-like projection called the uvula along the midline.

From the base of the uvula, two vertical folds of tissue originate and descend downwards.

The anterior fold is called the anterior pillar, or the palatoglossal arch, and contains fibers of the palatoglossal muscle, which attaches to the sides of the tongue.

The posterior fold is called the posterior pillar, or the palatopharyngeal arch, and contains the palatopharyngeus muscle, which attaches to the lateral wall of the pharynx.

The action of these muscles helps the soft palate to perform two distinct functions; first, closure of the oropharyngeal isthmus and sealing the oral cavity from the oropharynx; and second, closure of the oropharynx from the nasopharynx, this occurs during the act of swallowing, preventing food from being pushed up to the nasopharynx and nasal cavity.

Next, let’s take a look at the floor of the mouth, which is the space between the base of the tongue and the inner aspect of the mandible.

It is formed by a layer of mucosa overlying a muscular diaphragm formed by a pair of mylohyoid muscles, which extends from the mandible to the hyoid bone.

Overlying the mylohyoid is the geniohyoid muscle along the center and the sublingual salivary gland along the periphery.

On the surface, the mucosa gives off a thin fold along the midline called the lingual frenulum that attaches to the lower surface of the tongue.