Structure and Origin - The anterior ethmoidal nerve is a terminal branch of the nasociliary nerve, which is a branch of the ophthalmic nerve (CN V). - It branches near the medial wall of the orbit. - It passes through the anterior ethmoidal canal alongside the anterior ethmoidal artery and vein. - It emerges in the anterior cranial fossa through the anterior ethmoidal foramen. - Within the cranial cavity, it passes along a groove upon the superior surface of the cribriform plate and descends through an aperture situated lateral to the crista galli to reach the nasal cavity.

Course - The anterior ethmoidal nerve passes through the anterior ethmoidal canal alongside the anterior ethmoidal artery and vein. - It emerges in the anterior cranial fossa through the anterior ethmoidal foramen. - Within the cranial cavity, it passes along a groove upon the superior surface of the cribriform plate. - It descends through an aperture situated lateral to the crista galli to reach the nasal cavity. - In the nasal cavity, it passes along a groove upon the internal aspect of the nasal bone and issues the medial and lateral internal nasal branches.

Distribution - Within the anterior cranial fossa, the anterior ethmoidal nerve provides sensory fibers to the meninges for sensory innervation. - Its medial internal nasal branch innervates the superior and anterior portions of the nasal septum. - Its lateral internal nasal branch innervates the anterior portion of the lateral nasal wall. - It gives off branches to the roof of the nasal cavity and bifurcates into a lateral internal nasal branch and medial internal nasal branch. - Its terminal branch, the external nasal nerve, innervates the skin of the nose between the nasal bones superiorly and the tip of the nose inferiorly.

Function - The anterior ethmoidal nerve is involved in the diving reflex.

Relationship with other nerves - The anterior ethmoidal nerve is a branch of the nasociliary nerve, which is a branch of the ophthalmic nerve (CN V). - The ophthalmic nerve is a branch of the trigeminal nerve (CN V).