Facial Nerve in Dentistry

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Questions and Answers

Which of the following best describes the origin of the Facial nerve?

It emerges from the cerebellum.

It emerges from the spinal cord.

It emerges from the corpus callosum.

It emerges from the brain between the pons and medulla. (correct)

What is the main function of the motor root of the Facial nerve?

Transmit sensory information from the external ear.

Taste sensation from the anterior tongue.

Stimulate saliva production.

Control facial expressions and some muscles. (correct)

What is the function of the chorda tympani?

Carries parasympathetic fibers to the parotid gland

Supplies the orbicularis oris muscle

Innervates the posterior 1/3 of the tongue

Innervates the anterior 2/3 of the tongue with taste sensation (correct)

Which branch of the Facial nerve is responsible for tast sensation from the anterior two-thirds of the tongue?

Chorda tympani. Signup and view all the answers

Which branch of the facial nerve provides innervation to the muscles of the lower lip?

Mandibular branch Signup and view all the answers

Which anatomical course of the Facial nerve occurs after it exits the cranial cavity?

Extracranial course. Signup and view all the answers

Which of the following muscles is innervated by the temporal branch of the facial nerve?

Corrugator supercilii Signup and view all the answers

What type of fibers does the Greater petrosal nerve primarily consist of?

Parasympathetic fibers to mucous glands. Signup and view all the answers

The Facial nerve supplies significant structures relevant in dentistry. Which of the following is NOT among its functions?

Providing sensation to the teeth. Signup and view all the answers

Which facial nerve branch typically contributes to the innervation of muscles in the upper lip and nose?

Buccal branch Signup and view all the answers

What role does the nerve to stapedius play within the middle ear?

Modulates sound intensity by dampening loud noises. Signup and view all the answers

Which nerve innervates the intrinsic and extrinsic muscles of the outer ear?

Posterior auricular nerve Signup and view all the answers

Which gland is NOT influenced by the parasympathetic fibers of the Facial nerve?

Thyroid gland. Signup and view all the answers

What is the main role of the cervical branch of the facial nerve?

Controls platysma muscle for neck movement Signup and view all the answers

Where does the facial nerve exit the skull?

Stylomastoid foramen Signup and view all the answers

Which of the following muscles is NOT innervated by the facial nerve?

Sternocleidomastoid Signup and view all the answers

What is primarily affected by damage to the facial nerve?

Motor supply to the muscles of facial expression Signup and view all the answers

Which of the following is NOT a consequence of facial nerve damage?

Difficulty seeing in low light Signup and view all the answers

Which of the following could cause an intracranial lesion of the facial nerve?

Stroke Signup and view all the answers

What type of glands does the facial nerve provide parasympathetic innervation to?

Submandibular and sublingual salivary glands Signup and view all the answers

Which condition can cause paralysis of the muscles of facial expression due to extrinsic factors?

Parotid gland tumor Signup and view all the answers

Study Notes

Facial Nerve

The facial nerve (VII) is part of the oral and dental sciences module.
GDC Learning Outcomes include describing relevant dental, oral, craniofacial, and general anatomy, and explaining their application to patient management.
Intended learning outcomes include describing the facial nerve's function, outlining the anatomical regions it supplies, and explaining its relevance to dentistry.

Intended Learning Outcomes

Describe the function of the facial nerve (VII).
Outline the anatomical regions it supplies.
Explain the relevance of the facial nerve to dentistry.

Why do I need to know this?

Understanding the facial nerve is crucial for dental procedures and patient care.

Resources

Anatomy.tv
Acland's Video Atlas of Human Anatomy
Netter's Head and Neck Anatomy for Dentistry
TeachMe Anatomy

Intracranial

The facial nerve emerges from the pons and medulla of the brainstem.
It has two roots: a larger motor root and a smaller sensory root (nervus intermedius).
The roots pass into the internal auditory meatus.

Motor Root Functions

The motor root controls muscles of facial expression.

Function - Nervus intermedius

Important for special sensory functions like taste.
It controls the anterior two-thirds of the tongue.
It manages parasympathetic efferents.
It provides the parasympathetic output for salivary glands like the submandibular and sublingual glands, as well as tear glands.

Anatomical Course

The facial nerve has intracranial and extracranial components.
Intracranial refers to its path through the cranium.
Extracranial refers to its subsequent course through the face and neck outside the cranium.
The nerve leaves the cranium via the stylomastoid foramen.

Intracranial summary

The nerve originates in the pons area of the brainstem.
Two roots form: motor and sensory, which pass through the internal auditory meatus into the facial canal.

3 branches before leaving facial canal

Greater petrosal nerve—parasympathetic fibers to mucous glands of the nose, paranasal sinuses, and palate and the lacrimal glands.
Nerve to stapedius—motor fibers to the stapedius muscle for sound dampening in the middle ear.
Chorda tympani—special sensory fibers to the anterior two-thirds of the tongue (taste) and parasympathetic fibers to submandibular and sublingual glands.

Chorda tympani

Provides sensory innervation to the anterior two-thirds of the tongue, responsible for taste.
Travels with the lingual nerve (a branch of the trigeminal nerve).
Contains parasympathetic fibers that control the submandibular and sublingual salivary glands.

Extracranial

The facial nerve exits the cranium via the stylomastoid foramen.
Branches include:
Posterior auricular nerve
Posterior belly of the digastric muscle
Stylohyoid muscle
Temporal branch
Zygomatic branch
Buccal branch
Marginal mandibular branch
Cervical branch

Posterior Auricular Nerve

Is a motor nerve.
It elevates in front of the mastoid process.
Innervates intrinsic and extrinsic muscles of the outer ear.
Supplies the occipital part of the occipitofrontalis muscle.

Nerves to digastric and stylohyoid muscle

Facial branches

A memory device to recall the branches is provided (e.g., "Two Zebras Bit My Cat").
The branches are:
- Temporal
- Zygomatic
- Buccal
- Marginal mandibular
- Cervical

Muscles of Facial Expression

The facial nerve controls muscles responsible for facial expressions like smiling, frowning, and blinking

Temporal Branch

Leaves the superior surface of the parotid gland.
Crosses the zygomatic arch to reach the forehead.
Supplies auricular muscles, frontalis muscle, orbicularis oculi, and corrugator supercilii muscle.

Zygomatic Branch

Usually two parts: Upper and lower.
The upper part passes above the orbit, innervating the frontal belly of occipitofrontalis and orbicularis oculi.
The lower part runs below the orbit and innervates the lower part of orbicularis oculi, as well as upper lip and nasal muscles.

Buccal Branch

Usually two parts.
Supplies the orbicularis oris, buccinator, and zygomaticus muscles
Contributes to innervation of muscles of the upper lip and nose.

Mandibular Branch

Emerges from the lower border of the parotid gland.
Runs near the inferior border of the mandible.
Supplies muscles of the lower lip: depressor labii inferioris, depressor anguli oris, and mentalis.

Cervical Branch

Passes downward from the lower border of the parotid gland.
Supplies the platysma muscle.
Controls skin of the neck (noticeable vertical and horizontal ridges and depressions) and the pulling down of the mouth's corners during grimacing.

Damage to the facial nerve - Intracranial lesions

Intracranial lesions occur during the intracranial course of the facial nerve, proximal to the stylomastoid foramen.
Causes include:
- Infection (related to the external or middle ear)
- Stroke

Damage to the facial nerve - Extracranial lesions

Paralysis or severe weakness of the muscles of facial expression are symptoms.
Causes can include:
- Parotid gland pathology (e.g., tumor, parotitis, surgery).
- Infection of the nerve (particularly by the herpes virus).
- Local anaesthetic (rare).

Parotid gland tumour and surgery

This is a specific cause of extracranial facial nerve damage.

Trigeminal and facial nerve examination

A procedure to assess these nerves.

Summary

The facial nerve provides motor function to facial muscles.
The nerve has a minor sensory role related to tongue taste and parasympathetic control of salivary glands, glands in the nose, palate, and tear glands.

Quiz

A quiz on the facial nerve will test the understanding of the material covered.

References

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Description

This quiz focuses on the facial nerve (VII) as it pertains to oral and dental sciences. It covers fundamental aspects such as its function, the anatomical regions it supplies, and its significance in dental practice. Understanding this nerve is essential for effective patient management in dentistry.