Content:
Introduction 0:00
Facial nerve scheme 00:47
Functional Components 05:41
Facial nerve Nuclei 07:42
Facial nerve course 10:45
Intracranial branches 11:12
Extracranial branches 14:36
Clinical Relevance: 16:57
Recap 19:30
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Facial nerve is responsible for providing motor innervation to facial muscles, as well as taste (anterior 2/3 of the tongue) and producing saliva and tears
Functional Components of the Facial nerve:
- Special Visceral Efferent (SVE) fibers
○ Nucleus: Motor nucleus
○ Supply muscles of facial expression
- General Visceral Efferent (GVE) fibers
○ Nucleus:: Superior salivatory nucleus
○ To submandibular ganglion for salivary glands and pterygopalatine ganglion for the lacrimal gland
- Special Visceral Afferent (SVA) fibers
○ From the anterior 2/3 of the tongue to geniculate ganglion to nucleus of solitary tract
- General Somatic Afferent (GSA) fibers
○ External ear to geniculate ganglion to spinal nucleus of the trigeminal nerve.
Nuclei of the facial nerve:
- Motor nucleus of facial nerve (nucleus nervi facialis) - SVE fiebrs
○ a somatomotor nucleus for innervation of all facial muscles, platysma, stylohyoid and posterior belly of the digastric
- Superior salivatory nucleus (nucleus salivatorius superior) - GVE fibers
○ a visceromotor nucleus for parasympathetic innervation of the lacrimal gland, nasal glands, palatine glands, nasopharyngeal glands, submandibular gland, sublingual gland and lingual glands
- Gustatory nucleus (nucleus gustatorius) - SVA fibers
○ a special sensory nucleus for the nuclei of the solitary tract - receives impulses from the chorda tympani
- Spinal nucleus of trigeminal nerve (nucleus spinalis nervi trigemini) - GSA fibers
○ somatosensory fibres from the facial nerve synapse in this nucleus
Parts:
- Motor root/Facial Nerve (somatomotor fibers)
- Sensory root/Intermediate nerve (nervus intermedius)
○ Consists of visceromotor fibers (for glands) and special sensory fibers (taste)
Course:
1. within the brainstem, it turns around the nucleus of the abducens nerve and thus elevates the facial colliculus on the floor of the fourth ventricle
2. Leaves the pons at the pontocerebellar angle and runs in the posterior cerebral fossa
3. enters the internal acoustic canal and passes through the facial canal / Fallopian canal (canalis nervi facialis)
4. runs ventrolaterally in the labyrinthic part (pars labyrinthica), takes a 90° turn at the geniculum of the facial canal (geniculum canalis nervi facialis)
5. Runs further within the facial canal and leaves the skull via the stylomastoid foramen (foramen stylomastoideum)
6. enters the parotid gland, where it splits into inferior and superior branches, which form the parotid plexus (plexus intraparotideus), which gives rise to the terminal branches for the facial muscles
Intracranial branches
- Greater petrosal nerve (nervus petrosus major), comes out from the Geniculate ganglion (ganglion geniculi)
○ Reaches the pterygopalatine fossa where it terminates in the pterygopalatine ganglion - brings parasympathetic fibres from superior salivatory nucleus and some taste fibres to the pterygopalatine ganglion
- Nerve to stapedius (nervus stapedius)
- Chorda tympani
○ joins the lingual nerve to travel to the submandibular ganglion. Provide parasympathetic innervation for the submandibular and sublingual glands and the lingual glands in the anterior 2/3 of the tongue
Extracranial branches
- Stylohyoid branch ramus stylohyoideus)
- Digastric branch (ramus digastricus)
- Posterior auricular nerve (nervus auricularis posterior)
○ Occipital branch (ramus occipitalis)
○ Auricular branch (ramus auricularis)
- GSA fibers
- Branches forming the parotid plexus
○ Temporal branches (rami temporales)
○ Zygomatic branches (rami zygomatici)
○ Buccal branches (rami buccales)
○ Marginal mandibular branch (ramus marginalis mandibulae)
○ Cervical branch (ramus colli
Clinical relevance:
- Dorsal facial nucleus: supplies upper face muscle
- Ventral facial nucleus: supplies lower face muscle
- Upper motor neuron lesion causes paralysis of the middle and lower halves of the face because upper face is supplied by both hemispheres
- Lower motor neuron lesion: Paralysis of all muscles on ipsilateral side
○ Bell's Palsy: form of facial nerve palsy, mostly idiopatic cause. Thought to be caused by viral infection due to edema around this nerve.
Sources:
- Singh, I. (2017). Human neuroanatomy (10th ed.).
Helwany M, Bordoni B. Neuroanatomy, Cranial Nerve 1 (Olfactory). In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-
- Kozlowski, T. (2017). Memorix Anatomy: The Complete Study Guide. 2nd ed. Thieme Medical Publishers.
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