Oral Cavity & Tongue – Lecture Review

Introduction & Context

• Lecture opens with famous tongue-twisters (e.g., “She sells seashells…”) to highlight the complex, rapid tongue motions required for speech.

• Emphasizes that the tongue never truly twists; sensation comes from intricate, coordinated muscular contractions.

• Oral cavity functions:
  • Beginning of the digestive tract (mechanical digestion).
  • Alternate airway for respiration.
  • Resonating chamber & articulator for speech.

Gross Subdivisions of the Oral Cavity

1. Oral Vestibule

• Space deep to lips & cheeks but superficial to teeth & gums.

• Outer walls: lips anteriorly, buccal mucosa & cheeks laterally.

• Cheeks (= buccae):
  • Reinforced by buccinator muscle.
  • Contain buccal fat pads—especially prominent in infants (helps create suction during nursing).

• Numerous mucous glands lubricate vestibular walls.

• Oral fissure = gap between parted lips when mouth open; connects vestibule to exterior.

2. Oral Cavity Proper

• Space internal to teeth–gingiva semicircle and deep to vestibule.

• Continuous posteriorly with oropharynx.

Gingiva (Gums) & Periodontium

• Gingiva = fibrous tissue + mucous membrane, firmly anchored to alveolar processes by the periodontium.

Teeth – Types, Form & Function

(Each description applies bilaterally in both jaws.)

• 2 Incisors: spade-shaped; slice/bite.

• 1 Cuspid (Canine): pyramid-shaped; pierce & tear.

• 2 Premolars + 2 Molars: broad crowns; crush & grind.

• Third molar (wisdom tooth) erupts in late adolescence; frequently impacted due to limited jaw space ➔ common surgical extraction.

Palate – Roof of the Oral Cavity

Common Histology

• Internal lining: mucosa + dense fat & glandular tissue in fibrous matrix.

Hard Palate (Anterior)

• Bony plate = maxilla + palatine bones.

• Key landmarks:
  • Incisive fossa (posterior to central incisors) – transmits nasopalatine nerve.
  • Greater palatine foramen (medial to 3rd molar) – passage for greater palatine a. & n.
  • Lesser palatine foramen – passage for lesser palatine neurovascular bundle.

Soft Palate (Posterior)

• Anterior soft palate = fibrous aponeurosis; posterior part muscular with free inferior edge.

• Uvula hangs midline from free margin; easily visible when mouth open.

• Functional roles:
  • Early swallow: tenses with tongue to mold food bolus.
  • Later swallow: elevates & moves anteriorly to seal internal nares, preventing nasal regurgitation & blocking inspiration (try breathing while swallowing—fails due to this seal).

• Failure of seal → food/drink can reflux into nasopharynx during sudden cough/laugh.

Muscles of the Soft Palate

(All innervated by vagus via pharyngeal plexus except tensor veli palatini.)

• Levator veli palatini
  • Origin: petrous temporal bone + cartilaginous auditory tube.
  • Sling/hammock fibers insert on palate midline.
  • Elevates soft palate in late swallowing.

• Tensor veli palatini
  • Vertical fibers that hook around pterygoid hamulus (pulley) ➔ horizontal pull to tense palate.
  • Innervation: V_3 (mandibular branch of trigeminal).

• Palatoglossus
  • Creates palatoglossal fold.
  • Depresses palate or elevates tongue.

• Palatopharyngeus
  • Forms palatopharyngeal fold.
  • Depresses palate or elevates pharynx.

Palatine Tonsil & Clinical Note

• Tonsil sits in recess between palatoglossal & palatopharyngeal folds.

• Tonsillectomy: outpatient, treats recurrent pharyngitis & sleep apnea; minimal long-term immune deficit.
  • Major risk: hemorrhage from tonsillar branch of facial artery.
  • Performed less today vs. 1970s; evidence shows limited indications.

Neurovascular Supply of Palate

• Hard palate: greater palatine a./n.; anterior part via nasopalatine n. through incisive fossa (target for anesthetic block).

• Soft palate: lesser palatine a./n.

• Dental anesthesia:
  • Greater palatine nerve block for palatal procedures; site (anterior vs posterior) debated.
  • Posterior approach can transiently impair swallowing/speech by numbing palatal muscles.

Floor of the Oral Cavity – Suprahyoid Muscles

Mylohyoid

• Forms muscular diaphragm of mouth floor.

• Origin: mylohyoid line on mandible ➔ median raphe & hyoid.

• Innervation: nerve to mylohyoid (branch of V_3 before mandibular foramen).

• Actions (dependent on synergists):
  • Elevates hyoid (when jaw fixed).
  • Depresses mandible (when hyoid fixed by infrahyoids).
  • Tenses floor for tongue stability in speech/ingestion.

Geniohyoid

• Cylindrical muscle superior to mylohyoid; mental spine ➔ hyoid.

• Innervation: C1 fibers via hypoglossal.

• Works with mylohyoid to elevate hyoid or depress mandible.

Tongue – Surface Anatomy & Taste

• Two main parts: root (anchored) & body (mobile).

• Midline groove divides halves; terminal sulcus forms V-shape; apex hosts foramen cecum (embryonic thyroglossal duct remnant).
  • Patent duct ➔ thyroglossal cyst (most common midline neck mass <10 yrs).

Papillae (Taste Bud-Bearing Structures)

• Filiform – filamentous, widespread anteriorly.

• Fungiform – mushroom-shaped, interspersed with filiform.

• Vallate (Circumvallate) – large discs in row anterior to terminal sulcus; furrow contains taste receptors.

• Taste mechanism: dissolved food molecules bind chemoreceptors on dendritic endings ➔ complex flavor perception.

Musculature of the Tongue

Intrinsic Muscles

• Complex fibers in multiple planes; change shape (curl, flatten, narrow, lengthen) for bolus manipulation & phonation.

Extrinsic Muscles (all \text{hypoglossal} n. except palatoglossus)

• Genioglossus
  • Mental spine ➔ fan to root & body.
  • Bilateral contraction: protrudes tongue ("stick out your tongue").
  • Unilateral: deviates tongue toward opposite side.
  • Superior fibers also depress central tongue.

• Hyoglossus
  • Greater horn of hyoid ➔ lateral root.
  • Depresses & retracts tongue.

• Styloglossus
  • Styloid process ➔ superolateral root.
  • Retracts & elevates tongue.

• Palatoglossus
  • Soft palate ➔ posterolateral tongue; vagus-supplied (discussed earlier).

Sensory & Motor Innervation of Tongue

• Anterior 2⁄3 General Sensation: lingual nerve (branch of V_3).

• Anterior 2⁄3 Taste: chorda tympani (branch of facial) hitch-hikes on lingual n. + carries parasympathetics to submandibular & sublingual glands.

• Posterior 1⁄3 Sensation & Taste: glossopharyngeal n.

• Base of tongue (very posterior) taste: internal laryngeal branch of vagus.

• Motor to almost all muscles: hypoglossal n.

Arterial & Venous Supply of Tongue

• Lingual artery (external carotid) passes deep to hyoglossus.
  • Dorsal lingual branches → root.
  • Deep lingual branch → body/apex.

• Veins follow arteries → internal jugular vein.

Salivary Glands – Location, Ducts & Contribution

• Saliva functions: moisten cavity & food, contains salivary amylase (initiates carbohydrate digestion).

Clinical Correlates & Practical Points

• Wisdom-tooth impaction due to limited jaw room; surgical removal avoids crowding/infection.

• Tonsillectomy: risk of postoperative hemorrhage (tonsillar br. facial a.).

• Nerve blocks:
  • Incisive fossa block → nasopalatine n. (anesthetizes anterior palate & incisors).
  • Greater palatine block → posterior palate; placement affects comfort vs motor side-effects.

• Thyroglossal cyst: persistent thyroglossal duct from foramen cecum; presents as midline neck mass in children.

• Swallow vs. breathing: Elevated soft palate + laryngeal closure makes simultaneous inspiration nearly impossible.

• Accidental laughter/cough while eating: sudden reversal of bolus pressure can overcome soft-palate seal, forcing food/liquid into nasopharynx.

Summary

• Oral cavity is a multifunctional space initiating digestion, speech, and supplemental breathing.

• Structural components (vestibule vs proper cavity), detailed boundaries (teeth, gingiva, palate, floor), and complex neuromuscular setup enable sophisticated tasks from mastication to articulation of tongue twisters.

• Understanding innervation, blood supply, and clinical landmarks is essential for dental anesthesia, airway management, and ENT surgery.