Facial Nerve Anatomy and Function

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Questions and Answers

Which anatomical structure is associated with the second pharyngeal arch?

Stapes (correct)

Clavicle

Greater cornu of the hyoid bone

Coracoid process

Where is the facial motor nucleus located?

In the medulla oblongata

At the pontomedullary junction (correct)

In the thalamus

In the spinal cord

Which component derives conscious control from only the contralateral primary motor cortex?

Facial nucleus as a whole

Nucleus ambiguous

Inferior half of the nucleus (correct)

Superior half of the nucleus

Which muscle is NOT derived from the second pharyngeal arch?

Masseter Signup and view all the answers

How is the facial motor nucleus organized?

Divided horizontally into superior and inferior halves Signup and view all the answers

Which muscle is involved in facial expression derived from the second pharyngeal arch?

Orbicularis oculi Signup and view all the answers

Which structure is a part of the hyoid bone derived from the second pharyngeal arch?

Lesser cornu Signup and view all the answers

Which aspect of the facial nucleus receives bilateral control?

Superior half representing the upper face Signup and view all the answers

What type of paralysis results from lower motor neuron lesions of the facial nerve?

Upper and lower facial paralysis Signup and view all the answers

Which cranial nerve is responsible for facial nerve function?

CN VII Signup and view all the answers

Where does the facial nerve originate?

Pontomedullary region Signup and view all the answers

Which structure does the facial nerve NOT innervate?

Taste to the posterior 1/3 of the tongue Signup and view all the answers

What is the primary role of the special visceral efferent fibers of the facial nerve?

Innervate muscles of facial expression Signup and view all the answers

Which structure does the facial nerve loop around during its pathway?

Abducens nucleus Signup and view all the answers

What type of paralysis is caused by upper motor neuron lesions affecting the facial nerve?

Lower facial paralysis only Signup and view all the answers

Which of the following is NOT a function of the facial nerve?

Motor control of chewing muscles Signup and view all the answers

Through which foramen does the facial nerve exit the skull?

Stylomastoid foramen Signup and view all the answers

Which of the following is a general visceral efferent function of the facial nerve?

Secretion from the sublingual glands Signup and view all the answers

What type of sensory fibres join the facial nerve motor roots as they exit the nucleus?

Taste fibres from the rostral solitary nucleus Signup and view all the answers

What is the role of the greater petrosal nerve?

Supplies parasympathetic fibres to the lacrimal gland Signup and view all the answers

Which structure is the first branch of the facial nerve after the geniculate ganglion?

Greater petrosal nerve Signup and view all the answers

What happens in the case of a supranuclear lesion of the facial nerve?

Paralysis of the upper half of the face and lower half contralaterally Signup and view all the answers

Which branch does the facial nerve give off immediately after exiting the stylomastoid foramen?

Posterior auricular branch Signup and view all the answers

What condition is most commonly associated with a loss of taste, tear production, and facial movement in an infranuclear lesion?

Bell’s palsy Signup and view all the answers

Which facial nerve branch supplies the anterior 2/3 of the tongue with taste sensation?

Chorda tympani Signup and view all the answers

What is the main characteristic of an infranuclear lesion of the facial nerve?

Weakness in both upper and lower facial muscles Signup and view all the answers

What anatomical feature is described as the Z-shaped pathway of the facial nerve?

Facial canal Signup and view all the answers

Which cranial nerve structure carries exclusively motor fibres once it exits the skull?

Facial nerve Signup and view all the answers

After the parotid gland, what happens to the facial nerve?

It forms a plexus and divides into branches Signup and view all the answers

What role does the chorda tympani play in the facial nerve?

Provides parasympathetic fibres to the sublingual glands Signup and view all the answers

What is typically indicated by a pure loss of motor function to the upper and lower facial fields?

Extracranial pathology Signup and view all the answers

Study Notes

Facial Nerve (CN VII)

The facial nerve (CN VII) provides motor, sensory, and parasympathetic functions to head and neck structures.
Embryologically, it's associated with the second pharyngeal arch.
Bones derived from this arch include the stapes, styloid process, and lesser cornu of the hyoid bone.
Muscles associated with the second pharyngeal arch include facial expression muscles, occipitofrontalis, stylohyoid muscle, posterior belly of digastric, and stapedius.

Facial Nucleus

The facial motor nucleus is located at the pontomedullary junction, a paired structure in the brainstem.
The nucleus's superior half controls the superior half of the face, receiving input from both sides of the primary motor cortex.
The inferior half of the face is controlled by only the contralateral primary motor cortex.
Fibers loop around the abducens nerve, traveling to the brainstem's ventral surface.

Intracranial Facial Nerve

After leaving the cerebellopontine angle, the facial nerve roots (motor and sensory) enter the internal auditory meatus.
The internal auditory meatus (approx. 1cm long) leads to the Z-shaped facial canal (approx. 3 cm long).
The facial canal is a convergence point for the motor and sensory roots.
Three segments within the facial canal (labyrinthine, tympanic, mastoid) contain exiting branches.

Labyrinthine Segment

The geniculate ganglion arises within this segment, where the facial nerve bends (geniculum).
The greater petrosal nerve branches off, carrying parasympathetic fibers to the lacrimal gland.

Tympanic Segment

Facial nerve travels through the tympanic cavity

Mastoid Segment

The stapedius nerve and chorda tympani branch from the facial nerve here.
The chorda tympani carries taste information to the anterior 2/3 of the tongue and parasympathetic fibers to the sublingual and submandibular glands.

Extracranial Facial Nerve

The facial nerve exits the skull through the stylomastoid foramen.
It produces branches like the posterior auricular nerve, which supplies the occipital part of occipitofrontalis and auricular muscles.
Further branches innervate the posterior belly of digastricus and stylohyoid muscles.
Then it enters the parotid gland (without innervating it).
Within the parotid gland, the facial nerve divides into five motor branches, each supplying different facial expression muscles.

Clinical Relevance

Facial nerve damage can be supranuclear (above the facial nucleus) or infranuclear (below the nucleus).
Supranuclear lesions cause paralysis of only the contralateral lower face, whereas infranuclear (lower motor neuron) lesions cause paralysis in both upper and lower facial halves.

Key Points

Supranuclear lesions lead to contralateral lower facial weakness only.
Infranuclear (LMN) lesions cause paralysis in both upper and lower facial halves.

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Description

Explore the intricacies of the facial nerve (CN VII) and its significant role in motor, sensory, and parasympathetic functions. This quiz covers its embryological origins, associated structures, and the facial motor nucleus's control across the face. Test your knowledge on the anatomy and physiology of this crucial cranial nerve.