Facial nerve

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Facial nerve

The paired facial nerve (from Latin facies 'face', so “facial nerve”) is also called the seventh cranial nerve , N. VII . With reference to topographical conditions in the embryo , it is also referred to as the 2nd branchial arch nerve . The facial nerve carries sensory, sensory , motor and parasympathetic fibers and innervates large parts of the head.

The VII nerve enters with the VIII nerve from the cranial cavity into the opening of the internal auditory canal . In the long history by the temporal bone of separating from the main part of the facial nerve , a nerve intermedius called part with sensitive / sensory and parasympathetic fibers and is divided into the portions of greater petrosal nerve and chorda tympani on. For more precise identification, the entire VII. Cranial nerve is therefore also called the intermediate nerve .

origin

Selected structures of the middle and inner ear with cranial nerves VII and VIII.
1 vestibular nerve
2 cochlear
nerve 3 facial nerve
4 outer facial knee / Ggl. geniculi
5 chorda tympani
6 cochlea
7 semicircular canals
8 hammer handle
9 eardrum
10 eustachian tube

The motor nuclei ( nuclei motorii nervi facialis ) are located in the pons , i.e. in the metencephalon (hindbrain). Before the motor fibers connect with those of the other qualities, they circumnavigate the motor core of the abducens nerve , which is known as the "inner facial knee".

The parasympathetic nucleus of origin, the nucleus salivatorius superior , lies in the myelencephalon (afterbrain).

Temporal Bone Pyramid of Man with Facial Canal (No. 13)

The sensory fibers probably project from the periphery to the nucleus spinalis nervi trigemini and also to the nucleus pontinus nervi trigemini , while the sensory fibers are directed to the nucleus tractus solitarii .

The facial nerve occurs at the cerebellopontine angle together with the vestibulocochlear nerve on the surface of the brain and extends via the internal acoustic porus into the temporal bone , a part of the temporal bone that also houses the inner and middle ear . Within the petrous bone, it runs in a bony canal, which is why it is called the facial canal ( Canalis n. Facialis ). In this canal, the nerve makes a sharp turn from front to back. This kink is called the "outer facial knee". At this point a ganglion is activated, the geniculate ganglion . It contains the sensitive and sensory pseudounipolar nerve cell bodies of the facial nerve. It is comparable to the spinal ganglion of a spinal nerve .

The intermediate part separates from the facial nerve within the facial canal. In addition, the stapedius nerve is released . The remainder of the facial nerve exits the temporal bone through the stylomastoid foramen .

Intermedius nerve

The intermedius (the "in between", according to its spatial position on the brain surface between the facial nerve itself and the 8th cranial nerve ) has two main branches, with some motor fibers also attaching to its first main branch.

N. facialis and N. intermedius
(diagram of the branches)

Petrosal major nerve

The major petrosal nerve (“great petrous nerve”) originates in the geniculate ganglion and is parasympathetic, motor and sensory. It connects with sympathetic fibers of the deep petrosal nerve and runs as the pterygoid canal nerve to the pterygopalatine ganglion . In this ganglion, the preganglionic parasympathetic fibers are switched to postganglionic fibers and, together with the sympathetic fibers, mostly reach their successor organs using branches of the maxillary nerve :

The sensory fibers innervate the taste buds of the soft palate .

Chorda tympani

The chorda tympani (“drum string”) runs through the middle ear, leaves the skull at the petrotympanic fissure and has parasympathetic fibers that stimulate the secretion of the lower salivary glands (mandibular and sublingual glands) and the tongue glands (efferent). It uses it to conduct sensory taste stimuli from the front two thirds of the tongue .

Stapedius nerve

The stapedius nerve innervates the stapedius muscle (stapes muscle ) in the middle ear . This small muscle is one of the two muscles that influence the oscillation of the ossicular chain and thus reduce sound conduction - for example when there is a lot of noise. The facial nerve is thus also the efferent leg of the stapedius reflex . Increased sensitivity to sound ( hyperacusis ) can occur if the facial nerve and thus the stapedius nerve are damaged.

Facial branches

Course of the nerve branches

After exiting the stylomastoid foramen, the facial nerve pulls forward under the parotid gland and rises to the surface at the posterior margin of the lower jaw . There it is right under the skin. As a result, it is only slightly protected and can easily be damaged by external influences. This can lead to peripheral facial paralysis .

The following branches are given in detail:

  • Posterior auricular nerve (in animals caudal auricular nerve ): innervates the posterior muscles of the ear; has some sensitive fibers that innervate Hunt's zone
  • Internal auricular nerve : supplies the inside of the auricle in animals
  • Ramus digastricus : for the posterior abdomen ( venter posterior ) of the digastric muscle
  • Ramus stylohyoideus : for the stylohyoid muscle

The following branches motorically innervate the facial muscles and are regarded as branches from the intraparotide plexus , a plexus of nerves in the parotid gland :

See also

Web links

Commons : Facial nerve  - collection of images, videos and audio files
Wiktionary: Nervus facialis  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ↑ Federative Committee on Anatomical Terminology (1998). Terminologia Anatomica . Stuttgart: Thieme.

literature

  • Martin Trepel: Neuroanatomy. Structure and function. 3rd, revised edition. Urban & Fischer, Munich a. a. 2004, ISBN 3-437-41297-3 .
  • Franz-Viktor Salomon: nervous system, systema nervosum . In: Franz-Viktor Salomon, Hans Geyer, Uwe Gille (Ed.): Anatomy for veterinary medicine. Enke, Stuttgart 2005, ISBN 3-8304-1007-7 , pp. 464-577.