Anatomy of the oral cavity (dentistry)
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.
On either side of the lingual frenulum, there’s a tiny bump called the sublingual caruncula where the submandibular gland ducts, also known as the Wharton’s duct, open.
The tongue is a very flexible muscular organ that occupies most parts of the oral cavity proper. The tongue’s surface is covered by the mucosa, below which is a combination of intrinsic and extrinsic muscles.
Intrinsic muscles start and end within the tongue and help change its shape, while extrinsic muscles attach to structures outside the tongue and help guide its movement.
There’s a V-shaped groove on the tongue called the sulcus terminalis, which runs across its posterior portion and divides it into an anterior two-thirds and a posterior one-third.
The posterior third of the tongue extends down into the pharynx and it is covered in bumps made of lymphoid tissue called lingual papillae; these contain immune cells that help fight off pathogens entering the mouth.
The anterior two-thirds of the tongue resides in the oral cavity and it is covered in smaller lumps called papillae, which help increase the tongue’s surface area and give it a rough texture so food particles can stick to it.
The papillae contain multiple taste buds, and each taste bud contains specialized epithelial cells called taste receptor cells, which, yep, you guessed it!
detect taste. Although the majority taste buds are found on the tongue, some are also found on the soft palate, pharynx, epiglottis, larynx, and upper esophagus.
The upper lip extends up to the base of the nose, while the lower lip extends till just above the chin at the mento-labial sulcus.
The two lips meet at the angle of the mouth, at a point known as the labial commissure. From outside to inside, the lips are composed of skin, subcutaneous tissue, the orbicularis oris muscle fibers, and mucosa.
The orbicularis oris is a muscle that encircles the mouth and helps the lips move, especially while puckering the lips and whistling.
The reddish-pink colored part of the lip is called the vermilion. On the inner surface, a thin flap of the lip mucosa along the middle, called the labial frenulum, extends and attaches to the adjacent gums.
Next we have the gingiva,, which is a layer of supportive tissue that sits on top of the alveolar bone and is divided into two parts; the attached gingiva, which is connected to the alveolar process, and the free gingiva, which extends to the free gingiva margin surrounding the teeth like a collar.
The part of the free gingiva running in between the teeth is called the interdental papillae. Now, the teeth sit within the alveolar tooth sockets.
In our lifetime, we have a total of 20 deciduous teeth, and 32 permanent teeth. There are a few different types of teeth- the incisors, canines, premolars, and molars.
Each of these teeth has a different shape and specialized function for chewing food. Finally, the lateral walls of the oral cavity are formed by the cheeks.
Medially, the cheek begins at the nasolabial sulcus, which is a shallow depression running from the side of the nose to the angle of the mouth.
What makes the cheeks chubby is the presence of a buccal pad of fat beneath the skin and superficial fascia. Deep to the pad of fat is the buccopharyngeal fascia covering the buccinator muscle, and the innermost layer is the oral mucosa.
The parotid gland’s duct, called the Stensen’s duct, opens on the mucosal surface of the cheek, opposite to the upper second molar teeth.
##Summary All right, as a quick recap… the oral cavity is a space that extends from the inner surface of the lips to the beginning of the oropharynx.
It can be divided into two parts - the oral vestibule which lies in between the lips and the teeth; and the oral cavity proper, which lies between the back of the teeth and the oropharynx.
The oral cavity roof is formed by the hard palate in the anterior two-thirds and the soft palate in its posterior one-third.
The floor of the mouth is formed by the mucosa over the mylohyoid muscle, geniohyoid muscle, and the sublingual gland. The teeth sit within sockets in the alveolar process, cushioned on the outside by the gingiva.
Finally, the tongue is a flexible muscular organ occupying most of the oral cavity proper. It’s composed of a bunch of intrinsic and extrinsic muscles; and is covered by tiny bumps called papillae, which contain the taste buds.
proper. It's composed of a bunch of intrinsic and extrinsic muscles and is covered by tiny bumps called papillae which
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