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 pass ...

. 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 scal ...

(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 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. The nasal ...

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 (literal translation, lit. ''triplet'' nerve), also known as the fifth cranial nerve, cranial nerve V, or simply CN V, is a cranial nerve responsible for Sense, sensation in the face and motor functions ...

(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 a ...

. The anterior ethmoidal nerve arises only after the nasociliary has given off its four branches (the ramus communicans to the ciliary ganglion, the long ciliary nerves, the infratrochlear nerve, and the posterior ethmoidal nerve). It travels through the anterior ethmoidal foramen to reach the anterior cranial fossa. It then moves forward and passes through the cribriform plate 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 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 nasal septum. 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 op ...

References

Ophthalmic nerve {{neuroanatomy-stub