Chorda tympani

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Chorda tympani
Gray912.png
The left tympanic membrane with the malleus and the chorda tympani, viewed from within the tympanic cavity (medial).
Details
From Facial nerve
InnervatesTaste (anterior 2/3 of tongue)

Submandibular gland

Sublingual gland
Identifiers
Latin nervus chorda tympani
MeSH D002814
TA98 A14.2.01.084
A14.2.01.118
TA2 6292
FMA 53228
Anatomical terms of neuroanatomy

Chorda tympani is a branch of the facial nerve that carries gustatory (taste) sensory innervation from the front of the tongue and parasympathetic (secretomotor) innervation to the submandibular and sublingual salivary glands. [1]

Contents

Chorda tympani has a complex course from the brainstem, through the temporal bone and middle ear, into the infratemporal fossa, and ending in the oral cavity. [2]

Structure

Chorda tympani fibers emerge from the pons of the brainstem as part of the intermediate nerve of the facial nerve. The facial nerve exits the cranial cavity through the internal acoustic meatus and enters the facial canal. Within the facial canal, chorda tympani branches off the facial nerve and enters the lateral wall of the tympanic cavity within the middle ear, where it runs across the tympanic membrane (from posterior to anterior) and medial to the neck of the malleus. [3]

Chorda tympani then exits the skull by descending through the petrotympanic fissure into the infratemporal fossa. Here it joins the lingual nerve, a branch of the mandibular nerve (CN V3). Traveling with the lingual nerve, the fibers of chorda tympani enter the sublingual space to reach the anterior 2/3 of the tongue and submandibular ganglion. [4]

Function

The chorda tympani carries two types of nerve fibers from their origin from the facial nerve to the lingual nerve that carries them to their destinations:

Right chorda tympani nerve, viewed from lateral side Chorda tympani nerve.jpg
Right chorda tympani nerve, viewed from lateral side

Taste

The chorda tympani is one of three cranial nerves that are involved in taste. The taste system involves a complicated feedback loop, with each nerve acting to inhibit the signals of other nerves.

There are similarities between the tastes the chorda tympani picks up in sweeteners between mice and primates, but not rats. Relating research results to humans is therefore not always consistent. [5] Sodium chloride is detected and recognized most by the chorda tympani nerve. [5] The recognition and responses to sodium chloride in the chorda tympani is mediated by amiloride-sensitive sodium channels. [6] The chorda tympani has a relatively low response to quinine and varied responses to hydrochloride. The chorda tympani is less responsive to sucrose than is the greater petrosal nerve. [7]

Chorda tympani transection

The chorda tympani nerve carries its information to the nucleus of solitary tract, and shares this area with the greater petrosal, glossopharyngeal, and vagus nerves. [8] When the greater petrosal and glossopharyngeal nerves are cut, regardless of age, the chorda tympani nerve takes over the space in the terminal field. This takeover of space by the chorda tympani is believed to be the nerve reverting to its original state before competition and pruning. [9] The chorda tympani, as part of the peripheral nervous system, is not as plastic in early ages. In a study done by Hosley et al. and a study done by Sollars, it has been shown that when the nerve is cut at a young age, the related taste buds are not likely to grow back to full strength. [10] [11] In a bilateral transection of the chorda tympani in mice, the preference for sodium chloride increases compared to before the transection. Also avoidance of higher concentrations of sodium chloride is eliminated. [5] The amiloride-sensitive channels responsible for salt recognition and response is functional in adult rats but not neonatal rats. This explains part of the change in preference of sodium chloride after a chorda tympani transection. [6] The chorda tympani innervates the fungiform papillae on the tongue. [11] According to a study done by Sollars et al. in 2002, when the chorda tympani has been transected early in postnatal development some of the fungiform papillae undergo a structural change to become more “filiform-like”. [12] When some of the other papillae grow back, they do so without a pore. [11]

Dysfunction

Injury to the chorda tympani nerve leads to loss or distortion of taste from anterior 2/3 of tongue. [13] However, taste from the posterior 1/3 of tongue (supplied by the glossopharyngeal nerve) remains intact.

The chorda tympani appears to exert a particularly strong inhibitory influence on other taste nerves, as well as on pain fibers in the tongue. When the chorda tympani is damaged, its inhibitory function is disrupted, leading to less inhibited activity in the other nerves.[ citation needed ]

Additional images

Related Research Articles

<span class="mw-page-title-main">Parasympathetic nervous system</span> Division of the autonomic nervous system

The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of the autonomic nervous system, and sometimes considered an independent system.

<span class="mw-page-title-main">Salivary gland</span> Exocrine glands that produce saliva through a system of ducts

The salivary glands in many vertebrates including mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands, as well as hundreds of minor salivary glands. Salivary glands can be classified as serous, mucous, or seromucous (mixed).

<span class="mw-page-title-main">Facial nerve</span> Cranial nerve VII, for the face and tasting

The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue. The nerve typically travels from the pons through the facial canal in the temporal bone and exits the skull at the stylomastoid foramen. It arises from the brainstem from an area posterior to the cranial nerve VI and anterior to cranial nerve VIII.

Articles related to anatomy include:

<span class="mw-page-title-main">Glossopharyngeal nerve</span> Cranial nerve IX, for the tongue and pharynx

The glossopharyngeal nerve, also known as the ninth cranial nerve, cranial nerve IX, or simply CN IX, is a cranial nerve that exits the brainstem from the sides of the upper medulla, just anterior to the vagus nerve. Being a mixed nerve (sensorimotor), it carries afferent sensory and efferent motor information. The motor division of the glossopharyngeal nerve is derived from the basal plate of the embryonic medulla oblongata, whereas the sensory division originates from the cranial neural crest.

<span class="mw-page-title-main">Parotid gland</span> Major salivary gland in many animals

The parotid gland is a major salivary gland in many animals. In humans, the two parotid glands are present on either side of the mouth and in front of both ears. They are the largest of the salivary glands. Each parotid is wrapped around the mandibular ramus, and secretes serous saliva through the parotid duct into the mouth, to facilitate mastication and swallowing and to begin the digestion of starches. There are also two other types of salivary glands; they are submandibular and sublingual glands. Sometimes accessory parotid glands are found close to the main parotid glands.

<span class="mw-page-title-main">Submandibular gland</span> Human salivary gland

The paired submandibular glands are major salivary glands located beneath the floor of the mouth. In adult humans, they each weigh about 15 grams and contribute some 60–67% of unstimulated saliva secretion; on stimulation their contribution decreases in proportion as parotid gland secretion rises to 50%. The average length of the normal adult human submandibular salivary gland is approximately 27 mm, while the average width is approximately 14.3 mm.

<span class="mw-page-title-main">Sublingual gland</span> Major salivary glands in the mouth

The sublingual gland is a seromucous polystomatic exocrine gland. Located underneath the oral diaphragm, the sublingual gland is the smallest and most diffuse of the three major salivary glands of the oral cavity, with the other two being the submandibular and parotid. The sublingual gland provides approximately 3-5% of the total salivary volume.

<span class="mw-page-title-main">Otic ganglion</span> Parasympathetic ganglion of the head and neck

The otic ganglion is a small parasympathetic ganglion located immediately below the foramen ovale in the infratemporal fossa and on the medial surface of the mandibular nerve. It is functionally associated with the glossopharyngeal nerve and innervates the parotid gland for salivation.

<span class="mw-page-title-main">Hyoglossus</span> Muscle

The hyoglossus is a thin and quadrilateral extrinsic muscle of the tongue. It originates from the hyoid bone; it inserts onto the side of the tongue. It is innervated by the hypoglossal nerve. It acts to depress and retract the tongue.

<span class="mw-page-title-main">Geniculate ganglion</span> Collection of facial nerve neurons

The geniculate ganglion is a collection of pseudounipolar sensory neurons of the facial nerve located in the facial canal of the head. It receives fibers from the facial nerve. It sends fibers that supply the lacrimal glands, submandibular glands, sublingual glands, tongue, palate, pharynx, external auditory meatus, stapedius muscle, posterior belly of the digastric muscle, stylohyoid muscle, and muscles of facial expression.

<span class="mw-page-title-main">Lingual nerve</span> Human nerve relaying sense to the tongue

The lingual nerve carries sensory innervation from the anterior two-thirds of the tongue. It contains fibres from both the mandibular division of the trigeminal nerve (CN V3) and from the facial nerve (CN VII). The fibres from the trigeminal nerve are for touch, pain and temperature (general sensation), and the ones from the facial nerve are for taste (special sensation).

<span class="mw-page-title-main">Submandibular ganglion</span>

The submandibular ganglion is part of the human autonomic nervous system. It is one of four parasympathetic ganglia of the head and neck..

<span class="mw-page-title-main">Parasympathetic ganglia</span> Autonomic ganglia of the parasympathetic nervous system

Parasympathetic ganglia are the autonomic ganglia of the parasympathetic nervous system. Most are small terminal ganglia or intramural ganglia, so named because they lie near or within (respectively) the organs they innervate. The exceptions are the four paired parasympathetic ganglia of the head and neck.

<span class="mw-page-title-main">Intermediate nerve</span> Portion of the facial nerve

The intermediate nerve, nervus intermedius, nerve of Wrisberg or glossopalatine nerve is the part of the facial nerve located between the motor component of the facial nerve and the vestibulocochlear nerve. It contains the sensory and parasympathetic fibers of the facial nerve. Upon reaching the facial canal, it joins with the motor root of the facial nerve at the geniculate ganglion. Alex Alfieri postulates that the intermediate nerve should be considered as a separate cranial nerve and not a part of the facial nerve.

<span class="mw-page-title-main">Salivatory nuclei</span>

The salivatory nuclei are two parasympathetic general visceral efferent cranial nerve nuclei - the superior salivatory nucleus and the inferior salivatory nucleus - that innervate the salivary glands. Both are located in the pontine tegmentum of the brainstem.

<span class="mw-page-title-main">Outline of human anatomy</span> Overview of and topical guide to human anatomy

The following outline is provided as an overview of and topical guide to human anatomy:

<span class="mw-page-title-main">Lingual papillae</span> Structure giving the tongue its characteristic rough texture

Lingual papillae are small structures on the upper surface of the tongue that give it its characteristic rough texture. The four types of papillae on the human tongue have different structures and are accordingly classified as circumvallate, fungiform, filiform, and foliate. All except the filiform papillae are associated with taste buds.

<span class="mw-page-title-main">Outline of the human nervous system</span> Overview of and topical guide to the human nervous system

The following diagram is provided as an overview of and topical guide to the human nervous system:

References

  1. ↑ Morton, David A. (2019). The Big Picture: Gross Anatomy. K. Bo Foreman, Kurt H. Albertine (2nd ed.). New York. p. 246. ISBN   978-1-259-86264-9. OCLC   1044772257.{{cite book}}: CS1 maint: location missing publisher (link)
  2. 1 2 McManus, L J; Dawes, P J D; Stringer, M D (2011-08-03). "Clinical anatomy of the chorda tympani: a systematic review". The Journal of Laryngology & Otology. 125 (11): 1101–1108. doi:10.1017/S0022215111001873. ISSN   0022-2151. PMID   21810294. S2CID   38402170.
  3. ↑ Kwong, Y; Yu, D; Shah, J (August 2012). "Fracture mimics on temporal bone CT: a guide for the radiologist". AJR. American Journal of Roentgenology. 199 (2): 428–34. doi:10.2214/ajr.11.8012. PMID   22826408.
  4. ↑ Rao, Ashnaa; Tadi, Prasanna (2020-08-10). "Anatomy, Head and Neck, Chorda Tympani". NCBI Bookshelf. PMID   31536194 . Retrieved 2021-01-10.
  5. 1 2 3 Golden, G. J.; Ishiwatari, Y.; Theodorides, M. L.; Bachmanov, A. A. (2011). "Effect of Chorda Tympani Nerve Transection on Salt Taste Perception in Mice". Chemical Senses. 36 (9): 811–9. doi:10.1093/chemse/bjr056. PMC   3195788 . PMID   21743094.
  6. 1 2 Sollars, Suzanne I.; Bernstein, Ilene L. (1994). "Amiloride sensitivity in the neonatal rat". Behavioral Neuroscience. 108 (5): 981–7. doi:10.1037/0735-7044.108.5.981. PMID   7826520.
  7. ↑ Sollars, Suzanne I.; Hill, David L. (2005). "In vivorecordings from rat geniculate ganglia: Taste response properties of individual greater superficial petrosal and chorda tympani neurones". The Journal of Physiology. 564 (3): 877–93. doi:10.1113/jphysiol.2005.083741. PMC   1464453 . PMID   15746166.
  8. ↑ Standring, Susan (21 October 2020). Gray's anatomy : the anatomical basis of clinical practice. Elsevier. ISBN   978-0-7020-7705-0. OCLC   1202943188.
  9. ↑ Corson, S. L.; Hill, D. L. (2011). "Chorda Tympani Nerve Terminal Field Maturation and Maintenance is Severely Altered Following Changes to Gustatory Nerve Input to the Nucleus of the Solitary Tract". Journal of Neuroscience. 31 (21): 7591–603. doi:10.1523/JNEUROSCI.0151-11.2011. PMC   3117282 . PMID   21613473.
  10. ↑ Hosley, M. A.; Hughes, S. E.; Morton, L. L.; Oakley, B (1987). "A sensitive period for the neural induction of taste buds". The Journal of Neuroscience. 7 (7): 2075–80. doi:10.1523/JNEUROSCI.07-07-02075.1987. PMC   6568951 . PMID   3612229.
  11. 1 2 3 Sollars, Suzanne I. (2005). "Chorda tympani nerve transection at different developmental ages produces differential effects on taste bud volume and papillae morphology in the rat". Journal of Neurobiology. 64 (3): 310–20. doi:10.1002/neu.20140. PMC   4965235 . PMID   15898061.
  12. ↑ Sollars, Suzanne I.; Smith, Peter C.; Hill, David L. (2002). "Time course of morphological alterations of fungiform papillae and taste buds following chorda tympani transection in neonatal rats". Journal of Neurobiology. 51 (3): 223–36. doi:10.1002/neu.10055. PMC   4965232 . PMID   11984844.
  13. ↑ Cain, P.; Frank, M. E.; Barry, M. A. (1996). "Recovery of chorda tympani nerve function following injury". Experimental Neurology. 141 (2): 337–46. doi:10.1006/exnr.1996.0169. PMID   8812170. S2CID   23006967.
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