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The greater petrosal nerve (or greater superficial petrosal nerve) is a
nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons). Nerves have historically been considered the basic units of the peripheral nervous system. A nerve provides a common pathway for the Electrochemistry, electrochemical nerv ...
of the head mainly containing pre-ganglionic parasympathetic fibres which ultimately synapse in the pterygopalatine ganglion. It branches from the facial nerve (CN VII) and is derived from the parasympathetic part of the nervus intermedius component of CN VII, with its cell bodies located in the superior salivary nucleus. In the connective tissue substance of the foramen lacerum, the greater petrosal nerve unites with the ( sympathetic) deep petrosal nerve to form the nerve of the pterygoid canal (vidian nerve) which proceeds to the pterygopalatine ganglion. It forms part of a chain of nerves that provide secretomotor innervation to the
lacrimal gland The lacrimal glands are paired exocrine glands, one for each eye, found in most terrestrial vertebrates and some marine mammals, that secrete the aqueous layer of the tear film. In humans, they are situated in the upper lateral region of each o ...
and mucosal glands of nasal cavity and palate.


Structure


Origin


Parasympathetic component

Preganglionic parasympathetic fibres arise in the superior salivary nucleus of the pontine tegmentum. They join with general somatic sensory and special sensory fibres to form the nervus intermedius. The nervus intermedius exits the cranial cavity at the internal auditory meatus, and joins with the motor root of the facial nerve at the geniculate ganglion. While preganglionic parasympathetic fibres pass through the geniculate ganglion, they neither synapse, nor have their cell bodies located there. Preganglionic parasympathetic fibres exit the geniculate ganglion as the greater petrosal nerve.


Gustatory sensory component

The greater petrosal nerve also conveys some special sensory nerve fibres which carry gustatory (taste) sensory information from the palate that are relayed to the pterygopalatine ganglion by the lesser palatine nerves and are in turn conveyed to the geniculate ganglion by the greater petrosal nerve to synapse in the ganglion.


Course

The greater petrosal nerve enters the
petrous part of the temporal bone The petrous part of the temporal bone is pyramid-shaped and is wedged in at the base of the skull between the sphenoid and occipital bones. Directed medially, forward, and a little upward, it presents a base, an apex, three surfaces, and three ...
and travels anteromedially through it at a 45° angle. It emerges into the middle cranial fossa upon the anterosuperior surface of the bone through the hiatus for greater petrosal nerve alongside the petrosal branch of the
middle meningeal artery The middle meningeal artery (') is typically the third branch of the maxillary artery#First portion, first portion of the maxillary artery. After branching off the maxillary artery in the infratemporal fossa, it runs through the foramen spinosum t ...
. In the middle cranial fossa, the nerve is situated between the two layers of the dura mater and passes obliquely anterior-ward along a groove upon the floor of the fossa - the ''groove for the greater petrosal nerve'' - that is situated upon the anterosuperior aspect of the
petrous part of the temporal bone The petrous part of the temporal bone is pyramid-shaped and is wedged in at the base of the skull between the sphenoid and occipital bones. Directed medially, forward, and a little upward, it presents a base, an apex, three surfaces, and three ...
and anteromedial to the arcuate eminence, and adjacent and parallel to the lesser petrosal nerve and its own groove. The nerve passes deep to the trigeminal ganglion to reach the foramen lacerum. At the foramen lacerum, it unites with the (sympathetic) deep petrosal nerve, forming the nerve of the pterygoid canal (which continues anterior-ward through the pterygoid canal to reach the pterygopalatine fossa and form the pterygopalatine ganglion).


Clinical significance

During surgery of the middle cranial fossa, manipulation of the dura mater may damage the greater petrosal nerve, causing bleeding or swelling at the geniculate ganglion; this can compress the facial nerve and cause facial paralysis.


Additional images

File:Gray789.png, Course and connections of the
facial nerve 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 ta ...
in the
temporal bone The temporal bone is a paired bone situated at the sides and base of the skull, lateral to the temporal lobe of the cerebral cortex. The temporal bones are overlaid by the sides of the head known as the temples where four of the cranial bone ...
. File:Gray841.png, Sympathetic connections of the sphenopalatine and superior cervical ganglia. File:Head lateral gr petrosal nerve.jpg, Head lateral gr petrosal nerve File:Autonomic Innervation to the Lacrimal Gland (and other glands of the deep face).svg, Depicts nerve branches that are involved in the autonomic innervation of the
lacrimal gland The lacrimal glands are paired exocrine glands, one for each eye, found in most terrestrial vertebrates and some marine mammals, that secrete the aqueous layer of the tear film. In humans, they are situated in the upper lateral region of each o ...
. The terminal parts of the pathway are variable between individuals and differ for the other glands of the deep face.


References


External links

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University of Michigan Medical School "Dissector Answers - Ear and Nasal Cavity"
{{Authority control Facial nerve Cranial nerves Otorhinolaryngology