eRadiograph Volume 7: Imaging of Oral Cavity | Page 8

The oral cavity is the most ventral portion of the aerodigestive tract. It contains lips,
floor of mouth, oral tongue, buccal mucosa, upper and lower gingivae, hard palate,
and retromolar trigone. It is separated from oropharynx, which lies posterior to the oral
cavity by a ring of structures: the circumvallate papillae inferiorly, tonsillar pillars
laterally and soft palate superiorly.
The oral cavity is divided into two parts - a central portion known as the oral cavity
proper and lateral components on either side of the oral cavity proper known as
vestibules. The oral cavity proper contains the oral tongue, the floor is made up by the
floor of the mouth and inferior alveolar ridge, the roof by hard palate and superior
alveolar ridge and laterally by the maxillary and mandibular alveolus lined by gingival
mucosa.
The vestibule is lined laterally by buccal mucosa, medially by gingival mucosa, along the
maxillary and mandibular alveoli. The junction of the gingival and buccal mucosa is
referred to as the superior and inferior gingivobuccal sulcus. The lips mark the anterior
extent and the retromolar trigone the posterior extent.

The pterygomandibular raphe is a thick fascial band which lies just below the mucosa
of the retromolar trigone. It runs from the posterior mylohyoid line of the mandible to
the hook of hamulus of medial ptyergoid plates. The medial surface of the
ptyergomandibular raphe is covered by mucosa, laterally it is separated from the ramus
of the mandible by adipose tissue. Buccinator arises from ptyergomandibular raphe
anteriorly and superior pharyngeal constrictor arises posteriorly from the
ptyergomandibular raphe thus. Disease can spread along the pterygomandibular
raphe, anteriorly to the buccinator, thus the buccal space, masticator space, floor of
mouth, posteriorly via the superior pharyngeal constrictor to the oropharynx.
Tongue
The tongue is the centrepiece of the oral cavity and oropharynx!
The tongue has important functions - it enables taste, forms the food bolus for
deglutition and is critical for speech. The tongue is divided into two parts, an anterior
two thirds, which constitutes the mobile or oral portion and the posterior one third,
which constitutes base or pharyngeal portion that is a part of the oropharynx. The
anterior and posterior tongue are divided by the line of circumvallate papillae, which

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Imaging of Oral Cavity

The retromolar trigone is a triangular shaped mucosal surface, posterior to the last
mandibular molar. It covers the anterior surface of the ascending ramus of mandible.
Superiorly, it is limited by base of pterygoid plate. The retromolar trigone provides
easy access for neoplasms to spread posterior to the ramus of mandible, oropharynx,
masticator space, mandibular branch of trigeminal nerve and pterygomandibular
raphe, Anteriorly to buccal space, Inferiorly to the floor of mouth.