Chapter 37: Mouth Anatomy

The external bounds include the lips and cheeks, leading internally to the oropharynx at the anterior pillars of the fauces, with the oral space compartmentalized into the vestibule and the oral cavity proper. The muscular floor of the mouth is defined primarily by the mylohyoid muscles and is dominated by the tongue, a highly mobile organ utilized for taste and speech, whose central midline fold is known as the lingual frenulum; limited movement due to a restricted frenulum is clinically termed ankyloglossia. The tongue's surface is divided into anterior (oral) and posterior (pharyngeal) regions by the sulcus terminalis, and specialized mucosa covers the dorsum, featuring lingual papillae (including filiform, fungiform, and circumvallate types), with most types bearing taste buds. Extrinsic muscles, such as genioglossus (the main airway dilator), styloglossus, and hyoglossus, control the tongue's position, while intrinsic muscles refine its shape using muscular hydrostat principles; all are innervated by the hypoglossal nerve, except for palatoglossus. General sensation for the anterior two-thirds of the tongue is conveyed by the lingual nerve, while taste from this region travels via the chorda tympani, distinguishing it from the posterior third, which relies on the glossopharyngeal nerve for both general and taste sensation. The oral mucosa itself is stratified into non-keratinized lining mucosa (e.g., alveolar mucosa) and keratinized masticatory mucosa (e.g., gingivae and hard palate). A major focus is the teeth, which exist in deciduous and permanent dentitions, composed of enamel (the hard, outer crown covering), dentine (the yellowish bulk of the tooth), cementum (the root covering), and the vital dental pulp within the root canal. Vascular supply to the teeth and supporting periodontal ligament is derived from the superior and inferior alveolar arteries (branches of the maxillary artery), with sensory innervation from corresponding alveolar nerves; clinical considerations, such as using cone beam computed tomography (CBCT) prior to extracting mandibular third molars, are essential to minimize iatrogenic damage to the closely associated inferior alveolar and lingual nerves. Finally, the chapter examines the three pairs of major salivary glands (parotid, submandibular, sublingual) and minor glands, noting that saliva secretion is largely driven by parasympathetic innervation; obstruction in ducts can result in retention cysts, such as a ranula in the floor of the mouth, which may sometimes plunge into the neck via a hiatus in the mylohyoid muscle. Knowledge of the potential tissue spaces around the jaws (e.g., sublingual, pterygomandibular) is critical as they define the paths for the spread of dental abscesses, which can sometimes track dangerously, such as an upper canine abscess potentially involving the cavernous sinus.