The anterior ethmoidal nerve is a nerve of the

nose A nose is a protuberance in vertebrates that houses the nostrils, or nares, which receive and expel air for respiration alongside the mouth. Behind the nose are the olfactory mucosa and the sinuses. Behind the nasal cavity, air next passes ...

. It is a branch of the

nasociliary nerve The nasociliary nerve is a branch of the ophthalmic nerve, itself a branch of the trigeminal nerve (CN V). It is intermediate in size between the other two branches of the ophthalmic nerve, the frontal nerve and lacrimal nerve. Structure The na ...

, itself 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 ...

(V₁). It provides sensory innervation to some structures around the

nasal cavity The nasal cavity is a large, air-filled space above and behind the human nose, nose in the middle of the face. The nasal septum divides the cavity into two cavities, also known as fossae. Each cavity is the continuation of one of the two nostrils. ...

Structure

The anterior ethmoidal nerve is a terminal branch of the

, a branch of the

(CN V₁), 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 chew ...

(CN V). It branches near the medial wall of the

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as ...

. The anterior ethmoidal nerve arises only after the nasociliary has given off its four branches (the ramus communicans to the

ciliary ganglion The ciliary ganglion is a bundle of nerve parasympathetic ganglion located just behind the eye in the posterior orbit. It is 1–2 mm in diameter and in humans contains approximately 2,500 neurons. The ganglion contains postganglionic parasympath ...

, the

long ciliary nerves The long ciliary nerves are 2-3 nerves that arise from the nasociliary nerve (itself a branch of the ophthalmic branch (CN V1) of the trigeminal nerve (CN V)). They enter the eyeball to provide sensory innervation to parts of the eye, and sympat ...

, the

infratrochlear nerve The infratrochlear nerve is a branch of the nasociliary nerve, itself a branch of the ophthalmic nerve. Structure The nasociliary nerve terminates by bifurcating into the infratrochlear and the anterior ethmoidal nerves. The infratrochlear ne ...

, and the

posterior ethmoidal nerve The posterior ethmoidal nerve is a nerve of the orbit around the eye. It is a branch of the nasociliary nerve from the ophthalmic nerve (CN V1). It supplies sensation to the sphenoid sinus, the ethmoid sinus, and part of the dura mater in the ...

). It travels through the

anterior ethmoidal foramen The anterior ethmoidal foramen is a small opening in the ethmoid bone in the skull. Lateral to either olfactory groove are the internal openings of the anterior and posterior ethmoidal foramina (or canals). The anterior ethmoidal foramen, situa ...

to reach the

anterior cranial fossa The anterior cranial fossa is a depression in the floor of the cranial base which houses the projecting frontal lobes of the brain. It is formed by the orbital plates of the frontal, the cribriform plate of the ethmoid, and the small wings and fr ...

. It then moves forward and passes through the

cribriform plate In mammalian anatomy, the cribriform plate (Latin for lit. ''sieve-shaped''), horizontal lamina or lamina cribrosa is part of the ethmoid bone. It is received into the ethmoidal notch of the frontal bone and roofs in the nasal cavities. It supp ...

to enter the

. It gives off branches to the roof of the nasal cavity, and bifurcates into a lateral internal nasal branch and medial internal nasal branch. It sends sensory fibers to the anterior ethmoid air cells and the middle ethmoidal air cells. The anterior ethmoidal nerve then continues into the cranial cavity at the side of the cribiform plate of the ethmoid bone. It gives sensory fibers to the meninges. It then enters the nasal cavity via the nasal slit. Within the nose, it gives sensory fibers to the anterior part of the

nasal septum The nasal septum () separates the left and right airways of the nasal cavity, dividing the two nostrils. It is depressed by the depressor septi nasi muscle. Structure The fleshy external end of the nasal septum is called the columella or co ...

. The branches it gives rise to are called the internal/septal and external nasal branches of the anterior ethmoidal nerve, and the external branch ultimately innervates skin on the lateral sides of the nose.

Function

The anterior ethmoidal nerve supplies sensation to the

. It also supplies sensation to part of the meninges. It is involved in the

diving reflex The diving reflex, also known as the diving response and mammalian diving reflex, is a set of physiological responses to immersion that overrides the basic homeostatic reflexes, and is found in all air-breathing vertebrates studied to date. It o ...

References

Ophthalmic nerve {{neuroanatomy-stub