Tongue😊

 

Tongue

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  • Only Filiform devoid of taste buds
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Circumvallate Papillae

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Foliate Papillae:

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Tongue Muscles

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Development of tongue

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Anterior 2/3

  • Mesoderm of arch 1 gives rise to 3 thickenings
    • 2 lingual swellings
    • 1 tuberculum impar
  • These three thickenings fuse → form the anterior 2/3
  • Sensory innervation: Lingual branch of mandibular nerve
  • Taste: Chorda tympani nerve

Posterior 1/3

  • Mesoderm of arch 3 and 4 gives rise to a midline swelling
    • Forms Hypobranchial eminence
  • The hypobranchial eminence is divided into
    • Cranial (arch 3)
      • Gives rise to the posterior 1/3
      • Sensory and taste: Glossopharyngeal nerve
    • Caudal (arch 4)
      • Gives rise to the posterior-most part
      • Sensory innervation: Vagus nerve
      • Taste: Glossopharyngeal nerve

Sulcus terminalis

  • Differentiates anterior 2/3rd from posterior 1/3rd
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General Sensory Supply

  • Lingual nerve
  • Glossopharyngeal nerve
  • Vagus nerve

Classification

  • Extrinsic muscles – move tongue as a whole.
  • Intrinsic muscles – alter shape of tongue.

Extrinsic Muscles

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Muscle
Origin
Key Features
Genioglossus
Genoid tubercle of mandible
(inner aspect)
- Not a true tongue muscle
- Largest muscle of tongue
- Fan shaped
- Protrudes tongue
- Safety muscle of tongue
- Prevents tongue from falling back
Styloglossus
Styloid process
- Retracts and elevates tongue
Hyoglossus
Hyoid bone
- Depresses and retracts tongue
Palatoglossus
Palate
- Muscle of palate and tongue
- Not a true tongue muscle
  • Safety muscle of tongue — Genioglossus muscle
  • Safety muscle of larynx — Posterior cricoarytenoid muscle
    • Mnemonic: Pakka (PCA) muscle

Nerve Supply of tongue muscles

  • All muscles of tongue
    • Derived from myotome of occipital somites (Paraxial mesoderm)
    • Supplied by the hypoglossal nerve
    • Exception: Palatoglossus (from 4th pharyngeal arch) → SLN (Vagus N)
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Clinical Testing

  • Hypoglossus (CN 12)
    • Test: ask patient to protrude tongue
    • If lesion present: tongue deviates towards the affected side (ipsilateral deviation)
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  • Glossopharyngeal N (CN 9)
    • Test: pressure on soft palate/uvula
    • Also supply Glossopharyngeus
  • Circumvallate papillae
    • Present in the anterior 2/3rd part of the tongue
    • But special sensation carried by glossopharyngeal
  • Jugular canal
    • Carries the glossopharyngeal nerve (IX)
    • Fracture of the jugular canal
      • Loss of taste sensation in the posterior 1/3rd of the tongue