Anatomy of the Oral Cavity and Pharynx

Anatomy of the Oral Cavity and Pharynx

Anatomy of the Oral Cavity and Pharynx

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Oral Cavity - Entry Essentials

  • Definition: Extends from lips (cutaneous-vermilion junction) to palatoglossal arches.
  • Boundaries:
    • Anterior: Lips (orbicularis oris m.).
    • Posterior: Palatoglossal arches (anterior tonsillar pillars).
    • Superior: Hard palate (bony anterior 2/3), Soft palate (muscular posterior 1/3).
    • Inferior: Floor of mouth (mylohyoid m.), tongue.
    • Lateral: Cheeks (buccinator m.).
  • Subdivisions:
    • Vestibule: Between lips/cheeks and teeth/gingivae.
      • Parotid (Stensen's) duct opens opposite upper 2nd molar.
    • Oral Cavity Proper: Space internal to dental arches.
      • Contents: Tongue, teeth, gingivae.
      • Ducts: Wharton's (submandibular) at sublingual caruncle; Rivinus' (sublingual) on sublingual fold.
  • Lining: Stratified squamous epithelium (non-keratinized; keratinized on hard palate, tongue dorsum, gingiva). Sagittal view of oral cavity, nasal cavity, and pharynx

⭐ Stensen's duct (parotid) opens into vestibule opposite maxillary 2nd molar; a key landmark.

Tongue & Salivary Glands - Taste & Moisten

  • Tongue: Muscular organ for taste, speech, mastication, deglutition.
    • Parts: Oral (ant. 2/3), Pharyngeal (post. 1/3); separated by sulcus terminalis.
    • Muscles:
      • Intrinsic: Alter shape.
      • Extrinsic: Alter position (Genioglossus, Hyoglossus, Styloglossus, Palatoglossus). 📌 Mnemonic: Good Hygienic Students Practice.
    • Innervation (Motor): CN XII (Hypoglossal) to all except Palatoglossus (CN X - Vagus).
    • Innervation (Sensory):
      • Ant. 2/3: General - Lingual (V3); Taste - Chorda Tympani (VII).
      • Post. 1/3: General & Taste - CN IX (Glossopharyngeal).
      • Root/Epiglottis: CN X (Vagus).
    • Papillae: Filiform (touch, no taste), Fungiform (taste), Foliate (taste), Circumvallate (taste, Von Ebner's glands). Anatomy of the tongue and papillae
  • Salivary Glands: Produce saliva (~1-1.5 L/day).
    • Major Glands:
      • Parotid: Serous. Stensen's duct. CN IX (parasymp).
      • Submandibular: Mixed (serous > mucous). Wharton's duct. CN VII (parasymp).
      • Sublingual: Mixed (mucous > serous). Ducts of Rivinus/Bartholin's. CN VII (parasymp).
    • Minor Glands: Scattered, mainly mucous. Von Ebner's (serous, associated with circumvallate papillae).
    • Functions: Lubrication, digestion (amylase), immunity (IgA), taste.

⭐ Frey's Syndrome: Post-parotidectomy gustatory sweating/flushing due to aberrant CN IX nerve regeneration to sweat glands over the parotid area.

Pharynx - The Crossroads

  • Location & Extent: Musculomembranous tube (12-14 cm); base of skull to C6 (inferior border of cricoid).
  • Subdivisions:
    • Nasopharynx: Skull base to soft palate.
      • Contents: Adenoids (pharyngeal tonsil), Eustachian tube opening, Fossa of Rosenmüller.
      • Epithelium: Ciliated columnar.
    • Oropharynx: Soft palate to hyoid/epiglottis.
      • Contents: Palatine tonsils, lingual tonsil.
      • Waldeyer's Lymphatic Ring: Pharyngeal (adenoids), tubal, palatine, & lingual tonsils. 📌 (P.T.P.L.)
      • Epithelium: Non-keratinized stratified squamous.
    • Laryngopharynx (Hypopharynx): Hyoid/epiglottis to C6.
      • Contents: Piriform fossae, postcricoid region.
      • Epithelium: Non-keratinized stratified squamous. Sagittal view of pharynx and oral cavity anatomy
  • Muscles:
    • Outer Circular (Constrictors): Superior, Middle, Inferior. Propel bolus.
      • Killian's Dehiscence: Weakness between thyropharyngeus & cricopharyngeus (inferior constrictor); site of Zenker's diverticulum.
    • Inner Longitudinal: Stylopharyngeus, Salpingopharyngeus, Palatopharyngeus. Elevate pharynx/larynx.
  • Innervation:
    • Motor:
      • Most muscles: Pharyngeal plexus (CN X, cranial root of CN XI).
      • Stylopharyngeus: Exclusively CN IX.
    • Sensory: Nasopharynx (CN V2), Oropharynx (CN IX), Laryngopharynx (CN X - internal laryngeal n.).

    ⭐ The stylopharyngeus is the only muscle innervated by the glossopharyngeal nerve (CN IX).

  • Oral cavity proper: Bounded by teeth/alveolar arches, palate, floor of mouth muscles.
  • Waldeyer's ring: Lymphoid tissue: pharyngeal, tubal, palatine, lingual tonsils.
  • Tongue motor: CN XII (not palatoglossus: CN X). Sensory: Ant 2/3rd Lingual (V3), Chorda tympani (VII); Post 1/3rd CN IX.
  • Pharynx: Nasopharynx (Eustachian tube), Oropharynx (palatine tonsils), Laryngopharynx (to cricoid).
  • Killian's dehiscence: Inferior constrictor weak spot for Zenker's diverticulum.
  • Palatine tonsil artery: Mainly tonsillar branch of facial artery.
  • Retropharyngeal space: Infection can spread to mediastinum.

Practice Questions: Anatomy of the Oral Cavity and Pharynx

Test your understanding with these related questions

A patient after a road traffic accident presents to the emergency room with difficulty in swallowing and slurred speech. Investigations reveal fractures in the occipitotemporal region. Which of the following areas should be tested in order to find the nerve which is involved?

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Flashcards: Anatomy of the Oral Cavity and Pharynx

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The most common cranial nerve involved in Nasopharyngeal carcinoma is _____th nerve

TAP TO REVEAL ANSWER

The most common cranial nerve involved in Nasopharyngeal carcinoma is _____th nerve

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