Tympanic nerve
| Tympanic nerve | |
|---|---|
| File:Gray791.png Plan of upper portions of glossopharyngeal, vagus, and accessory nerves. (Tympanic nerve visible in upper right) | |
| File:Gray779.png Tympanic nerve (labelled right side) | |
| Details | |
| To | Tympanic plexus |
| Identifiers | |
| Latin | nervus tympanicus |
| TA98 | Lua error in Module:Wikidata at line 746: attempt to index field 'wikibase' (a nil value). |
| TH | {{#property:P1694}} |
| TE | {{#property:P1693}} |
| FMA | {{#property:P1402}} |
| Anatomical terms of neuroanatomy [[[d:Lua error in Module:Wikidata at line 865: attempt to index field 'wikibase' (a nil value).|edit on Wikidata]]] | |
The tympanic nerve (Jacobson's nerve) is a branch of the glossopharyngeal nerve passing through the petrous part of the temporal bone to reach the middle ear. It provides sensory innervation for the middle ear, the Eustachian tube, the parotid gland, and mastoid cells. It also carries parasympathetic fibers destined for the parotid gland.
Structure
[edit | edit source]The tympanic nerve contains sensory axons to the middle ear (including the internal surface of the tympanic membrane) whose cell bodies are lodged in the superior ganglion of the glossopharyngeal nerve.[1][verification needed]
It also contains parasympathetic axons which continue as the lesser petrosal nerve to the otic ganglion, which itself gives off postganglionic parasympathetic neurons.[1][verification needed]
Origin
[edit | edit source]The tympanic nerve arises from the inferior ganglion of the glossopharyngeal nerve (CN IX)[1] in the jugular fossa.[2]
Course
[edit | edit source]It passes through the petrous part of the temporal bone within the tympanic canaliculus that is situated within the bony ridge separating the carotid canal and the jugular foramen to reach the middle ear.[2]
In the tympanic cavity of the middle ear, it ramifies upon the promontory of tympanic cavity to form the tympanic plexus.[2][1][verification needed]
Distribution
[edit | edit source]Sensory
[edit | edit source]The tympanic nerve provides sensation to the middle ear (tympanic cavity).[1] This includes the internal surface of the tympanic membrane. It also supplies the Eustachian tube, the parotid gland, and mastoid air cells.[1]
Parasympathetic autonomic
[edit | edit source]The tympanic nerve is also the parasympathetic root of the otic ganglion.[1][3] These neurons then provide secretomotor innervation of the parotid gland via the auriculotemporal nerve.[1] It is involved in the salivatory reflex to increase salivation during chewing.[4]
Variation
[edit | edit source]The tympanic nerve usually arises from the inferior ganglion of the glossopharyngeal nerve. Rarely, it may arise from a higher part.[1][verification needed] Rarely, it may provide no parasympathetic fibres to the otic ganglion.[3]
Clinical significance
[edit | edit source]The tympanic nerve is involved in a reflex, where stimulation of the ear canal increases salivation.[4]
Cancer
[edit | edit source]The tympanic nerve may be involved by paraganglioma, in this location referred to as a glomus tympanicum tumour.[5] This causes a soft mass in the middle ear (tympanic cavity).[5] There may also be pulsatile tinnitus, hearing loss or hearing problems, and some cardiac abnormalities.[5]
History
[edit | edit source]The tympanic nerve is also known as the nerve of Jacobson, or Jacobson's nerve.[1]
Additional images
[edit | edit source]-
Lesser petrosal nerve
References
[edit | edit source]Public domain This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)
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External links
[edit | edit source]- Tympanic and Lesser petrosal nerve diagram
- cranialnerves at The Anatomy Lesson by Wesley Norman (Georgetown University) (IX)
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