Oral cavity

Boundaries and divisions of the oral cavity

Topographically, the oral cavity is bounded anteriorly by the lips, laterally by the cheeks, the roof is formed by the palate, and the muscular floor and tongue are located inferiorly. Posteriorly, this space is open and transitions into the pharynx via the isthmus of the fauces (isthmus faucium).

The jaws and the teeth erupting from them divide the oral cavity into two functional zones:

1. Oral vestibule (vestibulum oris) — the anterolateral part. This is a slit-like, horseshoe-shaped space bounded externally by the lips and cheeks, and internally by the gums and dental arches.
2. Oral cavity proper (cavitas oris propria) — the postero-internal part located behind the teeth.

Communication between the vestibule and the cavity proper occurs through natural clefts — the interdental spaces.

Oral vestibule: lips and cheeks

Lips (labia oris) are folds consisting primarily of striated muscle. They are covered by skin externally and mucous membrane internally. Three zones are distinguished in the structure of the lip: the cutaneous zone, the transitional zone (where the skin lacks a stratum corneum), and the mucosal zone.

The upper lip (labium superius) is separated from the cheek by the nasolabial sulcus, and in the midline on its cutaneous surface runs the philtrum (philtrum), ending in a tubercle. The lower lip (labium inferius) is bounded inferiorly by the horizontal mentolabial sulcus. At the corners of the mouth, the lips merge to form the commissures (commissurae labiorum). Upon transitioning to the gums, the mucosa forms folds — the frenula of the upper and lower lips (frenulum labii superioris et inferioris). Motor innervation is provided by the facial nerve, while sensation is supplied by branches of the infraorbital and mental nerves.

Cheeks (buccae) also have cutaneous and mucosal coverings. Within their thickness lies the buccinator muscle (m. buccinator), and between it and the masseter muscle lies the buccal fat pad (corpus adiposum buccae). The mucous membrane of the cheeks gradually transitions into the gums (gingivae).

Mucous membrane and glands

The mucous membrane of the oral cavity (tunica mucosa oris) forms various folds, frenula, and elevations. The submucosa of the lips is rich in small labial glands (glandulae labiales). The cheeks also contain their own glands: buccal glands (glandulae buccales), whose bodies lie between the bundles of the buccinator muscle, and molar glands (glandulae molares), located in the region of the last molar tooth.

Special attention should be paid to the ducts of the salivary glands:

• The duct of the parotid salivary gland (ductus parotideus) pierces the cheek and opens at the level of the upper second molar.
• On the floor of the oral cavity lies the sublingual caruncle (caruncula sublingualis), where the ducts of the submandibular and sublingual glands open.
• Extending from the caruncle is the sublingual fold (plica sublingualis).

Openings and canals of bony structures

To ensure the blood supply and innervation of the oral cavity, a system of openings and canals exists within the jaws and palate:

• From the nasal cavity, the nasopalatine nerve (n. nasopalatinus) emerges onto the hard palate, passing through the incisive canals/foramina (canales/foramina incisiva).
• The greater descending palatine artery and greater palatine nerve pass through the greater palatine canal (canalis palatinus major). They emerge into the oral cavity through the greater palatine foramen (foramen palatinum majus).
• Similarly, lesser palatine vessels and nerves emerge through the lesser palatine foramina (foramina palatina minora).
• The mandibular canal (canalis mandibulae) runs within the thickness of the mandible, into which the inferior alveolar vessels and nerve enter through the mandibular foramen (foramen mandibulae).
• On the facial surface of the mandible, the mental foramen (foramen mentale) opens, through which the mental artery, veins, and nerve emerge (a., vv., n. mentales).
• On the inner aspect of the mandible, the mylohyoid groove (sulcus mylohyoideus) is visible, along which run the artery and nerve branch of the same name.

Class and exam questions

What else to study on this topic

• Blood supply and innervation of the lips and cheeks
• Anatomy of the hard and soft palate
• Topography of the buccal fat pad
• Structural features of the mucosa of the floor of the oral cavity
• Canals and foramina of the maxilla and mandible

Other topics in the "Skull" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.