The geniculate ganglion (from

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

''genu'', for "knee") is a collection of pseudounipolar

sensory neuron Sensory neurons, also known as afferent neurons, are neurons in the nervous system, that convert a specific type of stimulus, via their receptors, into action potentials or graded potentials. This process is called sensory transduction. The cell ...

s of the facial nerve located in the facial canal of the

head A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple animals may ...

. It receives fibers from the facial nerve. It sends fibers that supply the lacrimal glands,

submandibular gland The paired submandibular glands (historically known as submaxillary glands) are major salivary glands located beneath the floor of the mouth. They each weigh about 15 grams and contribute some 60–67% of unstimulated saliva secretion; on stimula ...

sublingual gland The paired sublingual glands are major salivary glands in the mouth. They are the smallest, most diffuse, and the only unencapsulated major salivary glands. They provide only 3-5% of the total salivary volume. There are also two other types of sal ...

tongue The tongue is a muscular organ (anatomy), organ in the mouth of a typical tetrapod. It manipulates food for mastication and swallowing as part of the digestive system, digestive process, and is the primary organ of taste. The tongue's upper surfa ...

, palate,

pharynx The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its struc ...

, external auditory meatus, stapedius muscle, posterior belly of the

digastric muscle The digastric muscle (also digastricus) (named ''digastric'' as it has two 'bellies') is a small muscle located under the jaw. The term "digastric muscle" refers to this specific muscle. However, other muscles that have two separate muscle bellie ...

, stylohyoid muscle, and muscles of facial expression. The geniculate ganglion is one of several ganglia of the head and neck. Like the others, it is a bilaterally distributed structure, with each side of the face having a geniculate ganglion.

Structure

The geniculate ganglion is located close to the

internal auditory meatus The internal auditory meatus (also meatus acusticus internus, internal acoustic meatus, internal auditory canal, or internal acoustic canal) is a canal within the petrous part of the temporal bone of the skull between the posterior cranial fossa ...

. It is covered superiorly by the petrous part of the temporal bone (which is sometimes absent over the ganglion). The geniculate ganglion receives fibers from the motor, sensory, and

parasympathetic 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 t ...

components of the facial nerve. It the contains special sensory neuronal cell bodies for

taste The gustatory system or sense of taste is the sensory system that is partially responsible for the perception of taste (flavor). Taste is the perception produced or stimulated when a substance in the mouth reacts chemically with taste receptor ...

, from fibers coming up from the

through the chorda tympani and from fibers coming up from the roof of the palate through the

greater petrosal nerve The greater petrosal nerve (or greater superficial petrosal nerve) is a nerve in the skull that branches from the facial nerve; it forms part of a chain of nerves that innervate the lacrimal gland. The preganglionic parasympathetic axons of this ne ...

. Sensory and parasympathetic inputs are carried into the geniculate ganglion via the nervus intermedius. Motor fibers are carried via the facial nerve proper. The

, which carries preganglionic parasympathetic fibers, emerges from the anterior aspect of the ganglion. The motor fibers of the facial nerve proper and parasympathetic fibers to the submandibular and pterygopalatine ganglia do not synapse in the geniculate ganglion. The afferent fibers carrying pain, temperature, and touch from the posterior auricular nerve, as well as those carrying special sensory (taste) fibers from the tongue (via the chorda tympani), do not synapse in the geniculate ganglion. Instead, the cells of the geniculate ganglion relay the signal to the appropriate brainstem nucleus, much like the Dorsal root ganglion neurons relay signal to nuclei in the spinal cord.

Function

Via the geniculate ganglion, the facial nerve (CN VII) gives * parasympathetic innervation to: ** the lacrimal glands. ** the

s. ** the

s. * special sensory innervation to: ** the

for

. * general sensory innervation to: ** skin of the posterior ear * somatic (branchial) motor innervation to: ** the palate ** the

. ** the external auditory meatus ** the stapedius muscle. ** the posterior belly of the

. ** the stylohyoid muscle. ** muscles of facial expression.

Clinical significance

The geniculate ganglion is an important surgical landmark near the

. The geniculate ganglion may become

inflamed Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molecu ...

due to viral infection by herpes zoster virus.

Additional images

File:Gray788.png , Plan of the facial and intermediate nerves and their communication with other nerves.

References

External links