The nervus intermedius, or intermediate nerve, is the part of the facial nerve

Facial nerve

The facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity...

 (cranial nerve VII) located between the motor component of the facial nerve and the vestibulocochlear nerve

Vestibulocochlear nerve

The vestibulocochlear nerve is the eighth of twelve cranial nerves, and is responsible for transmitting sound and equilibrium information from the inner ear to the brain...

 (cranial nerve VIII). It contains the sensory

Sensory nerve

Sensory nerves are nerves that receive sensory stimuli, such as how something feels and if it is painful, smooth, rough, etc.They are made up of nerve fibers, called sensory fibers .Sensory neurons are neurons that are activated by sensory input Sensory nerves are nerves that receive sensory...

 and parasympathetic

Parasympathetic nervous system

The parasympathetic nervous system is one of the two main divisions of the autonomic nervous system . The ANS is responsible for regulation of internal organs and glands, which occurs unconsciously...

 fibers of the facial nerve. Upon reaching the facial canal

Facial canal

The facial canal is a Z-shaped canal running through the temporal bone from the internal acoustic meatus to the stylomastoid foramen. In humans it is approximately 3 centimeters long, which makes it the longest human osseous canal of a nerve...

, it joins with the motor root of the facial nerve at the geniculate ganglion

Geniculate ganglion

The geniculate ganglion is an L-shaped collection of fibers and sensory neurons of the facial nerve located in the facial canal of the head...

.

Parasympathetic fibers

The superior salivatory nucleus contains the cell bodies of parasympathetic axons within the nervus intermedius. These fibers reach the geniculate ganglion but do not synapse. Some of these preganglionic parasympathetic fibers persist within the greater petrosal nerve as they exit the geniculate ganglion and subsequently synapse with neurons in the pterygopalatine ganglion

Pterygopalatine ganglion

The pterygopalatine ganglion is a parasympathetic ganglion found in the pterygopalatine fossa. It is one of four parasympathetic ganglia of the head and neck....

. These postganglionic neurons send axon

Axon

An axon is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neuron's cell body or soma....

s that provide parasympathetic innervation to the lacrimal gland

Lacrimal gland

The lacrimal glands are paired almond-shaped glands, one for each eye, that secrete the aqueous layer of the tear film. They are situated in the upper, outer portion of each orbit, in the lacrimal fossa of the orbit formed by the frontal bone. Inflammation of the lacrimal glands is called...

.

The remaining preganglionic fibers continue as the mixed facial nerve proper as it extends through the facial canal. Before the nerve exits the skull via the stylomastoid foramen

Stylomastoid foramen

Between the styloid and mastoid processes of the temporal bone is the stylomastoid foramenIt is the termination of the facial canal, and transmits the facial nerve and stylomastoid artery.- Clinical Relevance :...

 and after the nerve to the stapedius muscle has branched off, the facial nerve gives off the chorda tympani nerve. This nerve exits the skull through the Petrotympanic fissure

Petrotympanic fissure

The petrotympanic fissure is a fissure in the temporal bone that runs from the temporomandibular joint to the tympanic cavity....

 and merges with the lingual nerve

Lingual nerve

The lingual nerve is a branch of the mandibular nerve , itself a branch of the trigeminal nerve, which supplies sensory innervation to the tongue...

, after which it synapses with neurons in the submandibular ganglion

Submandibular ganglion

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

. These postganglionic neurons provide parasympathetic innervation to the submandibular

Submandibular gland

The paired submandibular glands are salivary glands located beneath the floor of the mouth. In humans, they account for 70% of the salivary volume and weigh about 15 grams. Unstimulated in humans, the percentage contribution to whole saliva; ~25% Parotid, Submandibular and Sublingual ~ 67% and...

 and sublingual gland

Sublingual gland

The sublingual glands are salivary glands in the mouth.They lie anterior to the submandibular gland under the tongue, beneath the mucous membrane of the floor of the mouth.They are drained by 8-20 excretory ducts called the ducts of Rivinus....

s.

Sensory fibers

The sensory component of the nervus intermedius carries input about sensation from the skin of the external auditory meatus, from the mucous membrane

Mucous membrane

The mucous membranes are linings of mostly endodermal origin, covered in epithelium, which are involved in absorption and secretion. They line cavities that are exposed to the external environment and internal organs...

s of the nasopharynx

Nasopharynx

The nasopharynx is the uppermost part of the pharynx. It extends from the base of the skull to the upper surface of the soft palate; it differs from the oral and laryngeal parts of the pharynx in that its cavity always remains patent .-Lateral:On its lateral wall is the pharyngeal ostium of the...

 and nose

Human nose

The visible part of the human nose is the protruding part of the face that bears the nostrils. The shape of the nose is determined by the ethmoid bone and the nasal septum, which consists mostly of cartilage and which separates the nostrils...

, and taste

Taste

Taste is one of the traditional five senses. It refers to the ability to detect the flavor of substances such as food, certain minerals, and poisons, etc....

 from the anterior two-thirds of the tongue

Tongue

The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...

, floor of the mouth, and the palate

Palate

The palate is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but, in most other tetrapods, the oral and nasal cavities are not truly separate. The palate is divided into two parts, the anterior...

. The sensory information from the mucous membrane

Mucous membrane

The mucous membranes are linings of mostly endodermal origin, covered in epithelium, which are involved in absorption and secretion. They line cavities that are exposed to the external environment and internal organs...

s of the nasopharynx and palate is carried along the greater petrosal nerve, while the chorda tympani nerve (and lingual nerve) carries taste input from the anterior two-thirds of the tongue, floor of mouth, and palate.

The geniculate ganglion contains the cell bodies of the sensory component of the nervus intermedius.

Geniculate neuralgia

Geniculate neuralgia

Geniculate ganglionitis or Geniculate Neuralgia , also called nervus intermedius neuralgia, is a rare disorder that involves severe pain deep in the ear, that may spread to the ear canal, outer ear, mastoid or eye regions. GN may also occur in combination with trigeminal or glossopharyngeal...

is a pain syndrome associated with the nervus intermedius.

External links

• http://www.neuroanatomy.wisc.edu/virtualbrain/BrainStem/15Salivatory.html