Oral Cavity and Tongue: Comprehensive Anatomy for Dental Practice

Overview

The oral cavity (cavitas oris) is the entry point of the digestive system and the primary workspace of dentistry. It is divided by the dental arches into two continuous spaces: the vestibule, a slit between the lips/cheeks and the teeth/gingiva, and the oral cavity proper, bounded by the teeth anteriorly and laterally, the hard and soft palate superiorly, and the tongue and floor of the mouth inferiorly.

Vestibule

Bounded externally by the lips (orbicularis oris) and buccinator muscle.
The parotid duct (Stensen's duct) opens into the vestibule opposite the second upper molar — a key clinical landmark for identifying parotid pathology.
The vestibular sulcus is where local anesthetic infiltration is typically deposited for maxillary and mandibular anterior teeth.

Hard and Soft Palate

The hard palate is formed by the palatine processes of the maxillae (anterior 2/3) and the horizontal plates of the palatine bones (posterior 1/3).
The incisive foramen transmits the nasopalatine nerve and vessels; the greater and lesser palatine foramina transmit the corresponding neurovascular bundles supplying the palate — both are important injection sites for palatal anesthesia.
The soft palate is muscular (levator veli palatini, tensor veli palatini, palatoglossus, palatopharyngeus, musculus uvulae) and elevates during swallowing and speech to separate the oro- and nasopharynx.

Tongue: Muscular Architecture

The tongue is divided by a V-shaped sulcus terminalis into an anterior two-thirds (oral part) and posterior one-third (pharyngeal part).

Intrinsic muscles (superior/inferior longitudinal, transverse, vertical) alter the tongue's shape and have no bony attachment.

Extrinsic muscles alter its position, all innervated by the hypoglossal nerve (CN XII) except palatoglossus (vagus/pharyngeal plexus):

Genioglossus: protrudes the tongue; the most important muscle to test for CN XII palsy (tongue deviates toward the side of a lower motor neuron lesion).
Hyoglossus: depresses and retracts the tongue.
Styloglossus: elevates and retracts the tongue.
Palatoglossus: elevates the posterior tongue, forming the palatoglossal arch.

Tongue: Papillae and Innervation

Filiform papillae: most numerous, no taste buds, provide mechanical grip.
Fungiform papillae: mushroom-shaped, scattered on the anterior tip and margins, contain taste buds.
Circumvallate papillae: 8-12 large papillae just anterior to the sulcus terminalis, arranged in a V, surrounded by a moat drained by von Ebner's glands.
Foliate papillae: vertical folds on the posterolateral tongue.

Sensory innervation is famously split between general sensation and taste:

Anterior 2/3: general sensation via lingual nerve (CN V3); taste via chorda tympani (CN VII).
Posterior 1/3: both general sensation and taste via glossopharyngeal nerve (CN IX).
Extreme posterior (near epiglottis): vagus nerve (CN X), internal laryngeal branch.

Floor of the Mouth and Salivary Openings

The sublingual caruncle, on either side of the lingual frenulum, carries the openings of Wharton's duct (submandibular gland) and the major sublingual ducts.
The lingual frenulum connects the tongue to the floor of the mouth; an abnormally short frenulum causes ankyloglossia (tongue-tie), which can impair speech and infant feeding.

Clinical Relevance

Third molar (wisdom tooth) extraction places the lingual nerve at risk as it runs close to the lingual plate of the mandible near the third molar, superficial to the mylohyoid; injury causes ipsilateral tongue numbness or taste loss.
Ranula: a mucus retention cyst of the sublingual gland presenting as a bluish swelling in the floor of the mouth.
Ankyloglossia is assessed and, if functionally significant, corrected with a frenectomy or frenotomy.
Squamous cell carcinoma most commonly arises on the lateral border of the posterior tongue, an area that should always be inspected and palpated during oral examination.
Loss of taste with intact general sensation (or vice versa) on the anterior tongue helps localize lesions of the facial nerve versus the lingual nerve.