L 36 Oral Cavity & Pharynx – Comprehensive Lecture Notes

Oral Cavity – General Boundaries & Subdivisions

• Dental arches split the space into two compartments:
• Vestibule (U-shaped space between cheeks & gums; mucosa-lined)
• Gingivae = mucosa overlying maxillary & mandibular alveolar processes.
• Opening of parotid (Stensen) duct empties here.
• Oral cavity proper (medial to dental arches)
• Contents: tongue, submandibular & sublingual glands + their ducts.
• Boundaries
• Anterior/Lateral: dental arches
• Posterior: palatoglossal folds (muscles covered by mucosa) – mark junction with oropharynx
• Roof: palate (hard + soft) covered by mucosa & mucous glands
• Floor: mylohyoid & geniohyoid mm.; mucosa-covered inside the mouth

Palate

• Hard palate (anterior, bony)
• Sensory nn.: greater palatine & nasopalatine (both CN V2)
• Blood: greater palatine a. (branch of descending palatine / maxillary) + sphenopalatine a.
• Soft palate (posterior, muscular valve)
• Functions
• Elevates to seal nasopharynx from oropharynx
• Depresses to close oropharyngeal isthmus from oral cavity
• Sensory nn.: lesser palatine (CN V2) + glossopharyngeal (CN IX)
• Blood: lesser palatine a. (from descending palatine)
• Muscles of soft palate (all insert into palatine aponeurosis)
• Tensor veli palatini – CN V3 – tenses soft palate & opens auditory tube
• Levator veli palatini – CN X – elevates soft palate
• Musculus uvulae – CN X – shortens & lifts uvula
• Palatoglossus – CN X – elevates tongue, pulls soft palate toward tongue

Skeleton of the Jaws

• Upper (maxilla + palatine bones)
• Alveolar process houses upper teeth.
• Palatine processes form anterior hard palate.
• Incisive foramina carry nasopalatine nn. (CN V2) & sphenopalatine branches.
• Horizontal plates of palatine bones complete posterior hard palate.
• Greater/Lesser palatine foramina open posterior hard palate → transmit greater/lesser palatine nn. & aa.
• Lower (mandible)
• Body, ramus, coronoid & condylar processes.
• Alveolar process houses lower teeth.
• Mandibular foramen → inferior alveolar n. (CN V3) & a.
• Mental foramen → mental n. (CN V3) & a.

Dentition

• Tooth parts: crown, neck, root, pulp cavity.
• Deciduous set = $20$ teeth (2 incisors, 1 canine, 2 molars / quadrant).
• Permanent set = $32$ teeth (2 incisors, 1 canine, 2 premolars, 3 molars / quadrant).
• Innervation
• Maxillary teeth → superior alveolar nn. (CN V2)
• Mandibular teeth → inferior alveolar nn. (CN V3)
• Blood
• Superior alveolar aa. from maxillary & infra-orbital aa.
• Inferior alveolar a. from maxillary a.

Tongue

• Covered by mucosa; sulcus terminalis separates anterior oral part from posterior pharyngeal part.
• Anterior – lingual papillae (taste buds)
• Posterior – lingual tonsils in oropharynx
• Ventral surface anchored by lingual frenulum.
• Intrinsic mm. (longitudinal, transverse, vertical) – change shape; all CN XII.
• Extrinsic mm. – change position (Table below)
• Palatoglossus – elevates tongue – CN X
• Styloglossus – retracts tongue – CN XII
• Hyoglossus – depresses & retracts – CN XII
• Genioglossus – depresses, protrudes (anterior pull) – CN XII
• Sensory supply
• General
• Lingual n. (CN V3): anterior $\frac{2}{3}$
• Glossopharyngeal IX: posterior $\frac{1}{3}$ & soft palate
• Vagus X: root & laryngopharynx
• Taste
• Chorda tympani (CN VII) via lingual n.: anterior $\frac{2}{3}$
• CN IX: posterior $\frac{1}{3}$
• CN X: root
• Vascular
• Lingual a. (external carotid) → tongue & floor of mouth
• Lingual vv. visible sublingually → internal jugular v.
• Clinical – CN XII lesion → tongue deviates toward weak side on protrusion.

Salivary Glands

• Parotid (largest; over masseter, anterior to ear)
• Duct pierces cheek into vestibule.
• Parasymp: lesser petrosal n. (CN IX) → otic ganglion → auriculotemporal n. (CN V3).
• Symp: post-ganglionics from superior cervical ganglion along vessels.
• Submandibular (wraps mylohyoid posterior edge; duct opens beside lingual frenulum)
• Parasymp: chorda tympani (CN VII) joins lingual n. → submandibular ganglion → gland.
• Symp: along lingual a.
• Sublingual (deep to mucosa under tongue; many small ducts)
• Same visceral motor wiring as submandibular.
• Clinical – rapid sublingual absorption (e.g., nitroglycerin) via deep lingual vv.

Pharynx – Regions & Relationships

• Muscular half-cylinder from skull base → inferior cricoid (C6).
• Posterior to it = retropharyngeal space (infection highway to mediastinum).
• Divided internally into:
• Nasopharynx (choanae → soft palate)
• Auditory (pharyngotympanic) tube opening; torus tubarius ridge.
• Tensor veli palatini opens tube to equalize pressure.
• Pharyngeal tonsil in roof; inflammation = adenoids → mouth breathing, ear infections.
• Oropharynx (soft palate → epiglottis)
• Oropharyngeal isthmus: bounded by palatoglossal folds (lateral), soft palate (roof), tongue (floor).
• Palatopharyngeal folds posterior; palatine tonsil sits in tonsillar fossa between folds.
• Lingual tonsils on dorsum tongue form anterior wall.
• Epiglottis guards laryngeal inlet; valleculae lie between tongue & epiglottis.
• Laryngopharynx (epiglottis → cricoid border)
• Communicates with larynx anteriorly; continuous with esophagus below.
• Piriform recesses lateral to inlet (common trapping spot for food/pills).

Pharyngeal Musculature

• All motor by CN X except: stylopharyngeus (CN IX) & tensor veli palatini (CN V3).
• External circular layer (constrictors) – attach posteriorly to midline raphe; sequential contraction propels bolus.
• Superior constrictor – anterior attachments: pterygoid hamulus, pterygomandibular raphe (buccinator), mandible, tongue root.
• Middle constrictor – stylohyoid lig. + hyoid → raphe.
• Inferior constrictor – thyroid & cricoid cartilages → raphe.
• Internal longitudinal layer – elevate/shorten pharynx & larynx (swallowing/vocalizing).
• Stylopharyngeus – styloid → thyroid cart.; CN IX.
• Palatopharyngeus – soft palate → thyroid cart./wall; CN X.
• Salpingopharyngeus – cartilage of auditory tube → blends with palatopharyngeus; CN X.

Swallowing (Deglutition)

• Stage 1 – voluntary: tongue pushes bolus into oropharynx.
• Stage 2 – involuntary, fast:
• Levator veli palatini lifts soft palate; tensor veli palatini tenses it → nasopharynx sealed.
• Tensor veli palatini also opens auditory tube.
• Suprahyoid & longitudinal pharyngeal mm. elevate larynx → epiglottis folds over inlet; bolus guided to piriform recesses.
• Stage 3 – involuntary: sequential contraction of constrictors drives bolus into esophagus.

Pharyngeal Neurovasculature

• Somatic motor – CN X (all palate/pharynx) except tensor veli palatini (CN V3) & stylopharyngeus (CN IX).
• Somatic sensory
• CN V2 branches – anterior/superior nasopharynx
• CN IX – soft palate, oropharynx, posterior nasopharynx
• CN X – laryngopharynx
• Arterial: multiple branches external carotid.
• Venous: pharyngeal venous plexus → internal jugular.
• Gag reflex – touch oropharynx → sensory CN IX, motor CN X.

Clinical Correlations (Summary)

• CN XII lesion → tongue deviates toward affected side.
• Sublingual drug route → rapid venous absorption.
• Adenoiditis (inflamed pharyngeal tonsil) → mouth breathing + auditory tube blockage.
• Retropharyngeal space infections can descend into thorax.

Study/Revision Prompts (from lecture)

• Contrast vestibule vs oral cavity proper boundaries.
• Nerve/artery patterns: maxillary vs mandibular territories.
• Pain loss anterior tongue → lingual n.? Taste loss → chorda tympani.
• Intrinsic vs extrinsic tongue muscles; which retract (styloglossus, hyoglossus), which protrude (genioglossus).
• Muscles sealing nasopharynx during swallow (levator & tensor veli palatini).
• Palatine tonsil location – between palatoglossal & palatopharyngeal folds.
• Auditory tube opened by tensor veli palatini → equalizes middle-ear pressure.

Practice Exam Answers (as provided)

1 – Lingual n. (CN V3) provides general sensation anterior $\frac{2}{3}$ (Ans D)
2 – Parotid duct opening lies in vestibule (Ans B)