Human Anatomy
Tongue
Tongue anatomy for MBBS: muscles, sensory, taste and motor nerve supply, papillae, development and lymphatic drainage, mapped to NMC codes AN39.1 and AN39.2.
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Tongue
Tongue anatomy for MBBS: muscles, sensory, taste and motor nerve supply, papillae, development and lymphatic drainage, mapped to NMC codes AN39.1 and AN39.2.
The tongue chapter covers its development, muscles, and the complex sensory, taste and motor nerve supply that reflects its arch origin. It underpins the clinical testing of the hypoglossal nerve, lingual cancer spread and thyroid development.
High-yield: Tongue
- The tongue is divided into an anterior two-thirds and a posterior third by the V-shaped sulcus terminalis.
- The anterior two-thirds develops from the first pharyngeal arch and the posterior third from the third arch.
- General sensation of the anterior two-thirds is carried by the lingual nerve, a branch of the mandibular nerve.
- Taste from the anterior two-thirds is carried by the chorda tympani, a branch of the facial nerve.
- Both general sensation and taste of the posterior third are carried by the glossopharyngeal nerve.
- A small area near the epiglottis is supplied by the internal laryngeal branch of the vagus.
- All the muscles of the tongue are supplied by the hypoglossal nerve except palatoglossus, which is supplied by the vagus.
- Genioglossus protrudes the tongue and is the muscle tested when the patient is asked to stick out the tongue.
- In a one-sided hypoglossal nerve palsy the protruded tongue deviates towards the paralysed side.
- The circumvallate papillae lie just in front of the sulcus terminalis and carry many taste buds.
- The filiform papillae are the most numerous and give the tongue its rough texture but carry no taste buds.
- The lymphatics of the tip of the tongue drain to the submental nodes, and the posterior third drains bilaterally to deep cervical nodes.
- Because the posterior third drains to both sides, cancer there can spread to lymph nodes on the opposite side of the neck.
- The foramen caecum at the apex of the sulcus terminalis marks the origin of the thyroid gland's descent.
Nerve supply of the tongue
- **Anterior two-thirds:** General sensation by lingual nerve, taste by chorda tympani from the facial nerve.
- **Posterior third:** Both general sensation and taste by the glossopharyngeal nerve.
- **Motor supply:** All muscles by the hypoglossal nerve, except palatoglossus by the vagus.
- **Clinical:** Hypoglossal palsy makes the protruded tongue point to the paralysed side.
NMC competencies in this chapter
- **AN39.1:** Gross features, muscles and nerve supply of the tongue
- **AN39.2:** Development, lymphatic drainage and applied anatomy of the tongue
Frequently Asked Questions
Why does the tongue deviate to one side in nerve palsy?
In a one-sided hypoglossal nerve palsy the genioglossus on the healthy side pushes the tongue across, so on protrusion it points towards the paralysed side.
How is taste supplied differently from sensation?
In the anterior two-thirds, general sensation runs in the lingual nerve while taste runs in the chorda tympani, whereas the posterior third has both carried by the glossopharyngeal nerve.
Why can tongue cancer spread to both sides of the neck?
The lymphatics of the posterior third and the midline drain bilaterally to the deep cervical nodes, so a tumour there can involve lymph nodes on the opposite side.
How does this chapter help in NEET-PG?
The dual sensory supply, hypoglossal testing and lingual lymphatics are examined in ENT, neurology and surgery, keeping the tongue high-yield for PG.
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