Tongue - Nerve Supply

Summary

This video explores the complex nerve innervation of the tongue, highlighting its diverse origins. The anterior 2/3 of the tongue is innervated by the lingual nerve for general sensation and chorda tympani for taste, except for the circumvallate papillae. The posterior 1/3 is served by the glossopharyngeal nerve for both sensations. The posteriormost part receives innervation from the internal lingual branch of the vagus nerve. The tongue's musculature, except for the palatoglossus muscle, is innervated by the hypoglossal nerve, with the palatoglossus being an exception due to its origin from the sixth branchial arch.

Takeaways

• 👅 The tongue has different nerve supplies depending on its parts: anterior 2/3, posterior 1/3, and the posterior most part.
• 🧠 The anterior 2/3 of the tongue's sensory supply is via the lingual nerve, a branch of the mandibular division of the trigeminal nerve (CN V).
• 🔟 The posterior 1/3 of the tongue's general sensation is carried by the glossopharyngeal nerve (CN IX).
• 🌐 The posterior most part of the tongue's general and taste sensations are served by the internal lingual branch of the vagus nerve (CN X).
• 👂 Taste sensation for the entire anterior 2/3 of the tongue is carried by the chorda tympani, a branch of the facial nerve (CN VII).
• 👅 The taste sensation for the circumvallate papilla and the posterior 1/3 of the tongue is handled by the glossopharyngeal nerve (CN IX).
• 💪 All muscles of the tongue, except for the palatoglossus, are innervated by the hypoglossal nerve (CN XII), which originates from the occipital myotomes.
• 🗣️ The palatoglossus muscle is an exception; it is innervated by the accessory nerve due to its origin from the mesenchyme of the sixth branchial arch.
• 🌱 The epithelium covering the anterior 2/3 of the tongue originates from the first branchial arch, while the posterior 1/3 comes from the third branchial arch, and the posterior most from the fourth branchial arch.
• 🧐 Understanding the embryological origins of different parts of the tongue helps in remembering their respective nerve supplies.

Q & A

What is the main reason why understanding nerve innervation to the tongue can be confusing?

Understanding nerve innervation to the tongue can be confusing due to the fact that different parts of the tongue have different sources or origins.

What are the three main parts of the tongue mentioned in the script?

The three main parts of the tongue are the body or anterior 2/3, the posterior 1/3, and the posterior most part.

Which branchial arch does the epithelium covering the anterior 2/3 of the tongue originate from?

The epithelium covering the anterior 2/3 of the tongue originates from the first branchial arch.

What nerve is responsible for the general sensation of the anterior 2/3 of the tongue?

The lingual nerve, which is a branch of the mandibular division of the trigeminal nerve (CN V), is responsible for the general sensation of the anterior 2/3 of the tongue.

Which cranial nerve provides general sensation to the posterior 1/3 of the tongue?

The glossopharyngeal nerve (CN IX) provides general sensation to the posterior 1/3 of the tongue.

What nerve carries out general and taste sensations for the posterior most part of the tongue?

The internal lingual branch of the vagus nerve (CN X) carries out both general and taste sensations for the posterior most part of the tongue.

Which nerve is responsible for taste sensation in the anterior 2/3 of the tongue, and what is an exception to this?

The chorda tympani, a branch of the facial nerve (CN VII), is responsible for taste sensation in the anterior 2/3 of the tongue, except for the circumvallate papillae.

What type of muscles does the tongue have, and which cranial nerve innervates them?

The tongue has intrinsic and extrinsic muscles, and all these muscles are innervated by the hypoglossal nerve (CN XII), except for the palatoglossus muscle.

Which muscle of the tongue has a different innervation compared to the others, and what is its innervation source?

The palatoglossus muscle has a different innervation source compared to the other muscles of the tongue; it is innervated by the cranial part of the accessory nerve.

Why is the innervation of the tongue muscles primarily by the hypoglossal nerve?

The muscles of the tongue have their origin from occipital myotomes, hence their innervation is chiefly by the hypoglossal nerve (CN XII).

How does understanding the origin of the tongue's parts help in remembering its innervation?

Understanding the origin of the tongue's parts helps in remembering its innervation because the nerves that supply these parts correspond to the branchial arches from which the parts originate.