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The nasociliary nerve is a branch of the
ophthalmic nerve The ophthalmic nerve (V1) is a sensory nerve of the face. It is one of three divisions of the trigeminal nerve (CN V). It has three branches that provide sensory innervation to the eye, the skin of the upper face, and the skin of the anterior sc ...
, itself a branch of the
trigeminal nerve In neuroanatomy, the trigeminal nerve ( lit. ''triplet'' nerve), also known as the fifth cranial nerve, cranial nerve V, or simply CN V, is a cranial nerve responsible for sensation in the face and motor functions such as biting and che ...
(CN V). It is intermediate in size between the other two branches of the ophthalmic nerve, the frontal nerve and lacrimal nerve.


Structure

The nasociliary nerve enters the orbit via the superior orbital fissure, between the two heads of the lateral rectus muscle and between the superior and inferior rami of the
oculomotor nerve The oculomotor nerve, also known as the third cranial nerve, cranial nerve III, or simply CN III, is a cranial nerve that enters the orbit through the superior orbital fissure and innervates extraocular muscles that enable most movements of ...
. It passes across the
optic nerve In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual information from the retina to the brain. In humans, the optic nerve is derived fro ...
(CN II) and runs obliquely beneath the
superior rectus muscle The superior rectus muscle is a muscle in the orbit. It is one of the extraocular muscles. It is innervated by the superior division of the oculomotor nerve (III). In the primary position (looking straight ahead), its primary function is elevat ...
and superior oblique muscle to the medial wall of the
orbital cavity In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents. In the adult human, the volume of the orbit is , ...
. It passes through the anterior ethmoidal opening as the anterior ethmoidal nerve and enters the cranial cavity just below the cribriform plate of the ethmoid bone. It supplies branches to the mucous membrane of the nasal cavity and finally emerges between the inferior border of the nasal bone and the side nasal cartilages as the external nasal branch.


Branches

* posterior ethmoidal nerve * anterior ethmoidal nerve * long ciliary nerves * infratrochlear nerve * communicating branch to ciliary ganglion


Function

The branches of the nasociliary nerve provide sensory innervation to structures surrounding the eye such as the cornea, eyelids, conjunctiva, ethmoid air cells and mucosa of the nasal cavity.


Clinical significance


Testing

Since both the short and long ciliary nerves carry the afferent limb of the
corneal reflex The corneal reflex, also known as the blink reflex or eyelid reflex, is an involuntary blinking of the eyelids elicited by stimulation of the cornea (such as by touching or by a foreign body), though it could result from any peripheral stimulus. ...
, one can test the integrity of the nasociliary nerve (and, ultimately, the
trigeminal nerve In neuroanatomy, the trigeminal nerve ( lit. ''triplet'' nerve), also known as the fifth cranial nerve, cranial nerve V, or simply CN V, is a cranial nerve responsible for sensation in the face and motor functions such as biting and che ...
) by examining this reflex in the patient. Normally both eyes should blink when either cornea (not the conjunctiva, which is supplied by the adjacent cutaneous nerves) is irritated. If neither eye blinks, then either the ipsilateral nasociliary nerve is damaged, or the facial nerve (CN VII, which carries the efferent limb of this reflex) is bilaterally damaged. If only the contralateral eye blinks, then the ipsilateral facial nerve is damaged. If only the ipsilateral eye blinks, then the contralateral facial nerve is damaged.


Additional images

File:Gray776.png, Nerves of the orbit. Seen from above. File:Gray778.png, Distribution of the maxillary and mandibular nerves, and the submaxillary ganglion. File:Gray787.png, Dissection showing origins of right ocular muscles, and nerves entering by the superior orbital fissure. File:Ciliary ganglion pathways.png, Pathways in the ciliary ganglion. File:Slide4abab.JPG, Extrinsic eye muscle. Nerves of orbita. Deep dissection.


References


External links

* - "A deeper dissection of the right orbit from a superior approach." * () * () * {{Authority control Ophthalmic nerve Medical mnemonics