The tympanic nerve (Jacobson’s nerve) is a branch of the

glossopharyngeal nerve 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 (closer to the nose) to the vagus nerve. ...

found near the ear. It gives sensation to the middle ear, the

Eustachian tube In anatomy, the Eustachian tube, also known as the auditory tube or pharyngotympanic tube, is a tube that links the nasopharynx to the middle ear, of which it is also a part. In adult humans, the Eustachian tube is approximately long and in d ...

, the

parotid gland 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 ma ...

, and

mastoid air cells The mastoid cells (also called air cells of Lenoir or mastoid cells of Lenoir) are air-filled cavities within the mastoid process of the temporal bone of the cranium. The mastoid cells are a form of skeletal pneumaticity. Infection in these cells ...

. It gives parasympathetic to supply to the parotid gland via the

otic ganglion 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 inn ...

and the auriculotemporal nerve.

Structure

The tympanic nerve arises from the inferior ganglion of the

. It ascends to the

tympanic cavity The tympanic cavity is a small cavity surrounding the bones of the middle ear. Within it sit the ossicles, three small bones that transmit vibrations used in the detection of sound. Structure On its lateral surface, it abuts the external auditor ...

through a small canal, the

inferior tympanic canaliculus The inferior tympanic canaliculus is a small passage of the tympanic branch of the glossopharyngeal nerve and inferior tympanic artery. In the bony ridge dividing the carotid canal from the jugular fossa is the small inferior tympanic canalicul ...

, on the under surface of the petrous portion of the

temporal bone The temporal bones are situated at the sides and base of the skull, and lateral to the temporal lobes of the cerebral cortex. The temporal bones are overlaid by the sides of the head known as the temples, and house the structures of the ears. ...

on the ridge which separates the

carotid canal The carotid canal is a passageway in the temporal bone of the skull through which the internal carotid artery enters the middle cranial fossa from the neck. Structure The carotid canal is located within the middle cranial fossa, at the petrous ...

from the

jugular fossa The jugular fossa is a deep depression in the inferior part of the temporal bone at the base of the skull. It lodges the bulb of the internal jugular vein. Structure The jugular fossa is located in the temporal bone, posterior to the carotid can ...

. In the tympanic cavity, it divides into branches which form the

tympanic plexus In the tympanic cavity, the tympanic nerve (a branch of CN IX) divides into branches which, along with sympathetic fibres from the carotid plexus, form the tympanic plexus. This plexus is located on the surface of the promontory. This tympanic p ...

and are contained in grooves upon the surface of the promontory. The tympanic nerve contains sensory axons to the

middle ear The middle ear is the portion of the ear medial to the eardrum, and distal to the oval window of the cochlea (of the inner ear). The mammalian middle ear contains three ossicles, which transfer the vibrations of the eardrum into waves in the ...

, including the internal surface of the

tympanic membrane In the anatomy of humans and various other tetrapods, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear from the middle ear. Its function is to transmit sound from the a ...

. Their cell bodies are found in the superior ganglion of the glossopharyngeal nerve. It also contains parasympathetic axons, which continue as the

lesser petrosal nerve The lesser petrosal nerve (also known as the small superficial petrosal nerve) is the general visceral efferent (GVE) component of the glossopharyngeal nerve (CN IX), carrying parasympathetic preganglionic fibers from the tympanic plexus to the p ...

to the

, which itself gives off postganglionic parasympathetic neurons.

Variation

The tympanic nerve usually arises from the inferior ganglion of the

. Rarely, it may arise from a higher part. Rarely, it may provide no parasympathetic fibres to the otic ganglion.

Function

The tympanic nerve provides sensation to the

(

). This includes the internal surface of the

. It also supplies the

, the

, and

. The tympanic nerve also gives parasympathetic supply to the

. These neurons then provide secretomotor innervation of the

via the auriculotemporal nerve. It is involved in the salivatory reflex to increase

salivation Saliva (commonly referred to as spit) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can ...

during

chewing Chewing or mastication is the process by which food is crushed and ground by teeth. It is the first step of digestion, and it increases the surface area of foods to allow a more efficient break down by enzymes. During the mastication process, th ...

Clinical significance

The tympanic nerve is involved in a reflex, where stimulation of the

ear canal The ear canal (external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear. The adult human ear canal extends from the pinna (anatomy), pinna to the eardrum and is about in length and in di ...

increases

Cancer

The tympanic nerve may be involved by

paraganglioma A paraganglioma is a rare neuroendocrine neoplasm that may develop at various body sites (including the head, neck, thorax and abdomen). When the same type of tumor is found in the adrenal gland, they are referred to as a pheochromocytoma. They a ...

, in this location referred to as a glomus tympanicum tumour. This causes a soft mass in the

(

). There may also be

pulsatile tinnitus Tinnitus is the perception of sound when no corresponding external sound is present. Nearly everyone experiences a faint "normal tinnitus" in a completely quiet room; but it is of concern only if it is bothersome, interferes with normal hearin ...

hearing loss Hearing loss is a partial or total inability to hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to acquire spoken l ...

or hearing problems, and some cardiac abnormalities.

History

The tympanic nerve is also known as the nerve of Jacobson, or Jacobson's nerve.

Additional images

File:Gray782_updated.png, Lesser petrosal nerve File:Gray843.png, Sympathetic connections of the otic and superior cervical ganglia.

References

External links

Tympanic and Lesser petrosal nerve diagram
* () {{DEFAULTSORT:Tympanic Nerve Glossopharyngeal nerve