The anterior ethmoidal artery is a branch of the ophthalmic artery that arises in the orbit and exits through the anterior ethmoidal foramen. It supplies blood to various structures in the head, such as the ethmoid sinuses, frontal sinuses, dura mater, lateral nasal wall, and nasal septum.

The anterior ethmoidal artery originates from the ophthalmic artery, which is a branch of the internal carotid artery. The ophthalmic artery enters the orbit through the optic canal along with the optic nerve. Within the orbit, it gives off several branches, including the posterior ethmoidal artery and the anterior ethmoidal artery.

The anterior ethmoidal artery is smaller than the posterior ethmoidal artery and runs more anteriorly in the orbit. It travels with the anterior ethmoidal nerve, which is a branch of the nasociliary nerve. The artery and nerve exit the orbit through the anterior ethmoidal foramen, which is an opening in the medial wall of the orbit near the frontoethmoidal suture.

After leaving the orbit, the anterior ethmoidal artery enters the anterior ethmoidal canal, which is a bony passage within the ethmoid bone. The artery gives off branches that supply the frontal sinus and the anterior and middle ethmoid air cells. The artery then enters the anterior cranial fossa, where it divides into a meningeal branch and a nasal branch.

The meningeal branch of the anterior ethmoidal artery ascends to supply some of the dura mater of the anterior cranial fossa. It has been called the anterior falx or falcine artery because it runs along the falx cerebri, which is a fold of dura mater that separates the cerebral hemispheres.

The nasal branch of the anterior ethmoidal artery descends through the cribriform plate of the ethmoid bone to enter the nasal cavity. It runs in a groove on the deep surface of the nasal bone and splits into a medial and a lateral branch. The medial branch supplies blood to the nasal septum, while the lateral branch supplies blood to the lateral wall of the nasal cavity. A terminal branch of the lateral branch, called the external nasal branch, passes between the nasal bone and the nasal cartilage to supply the skin of the nose.

The anterior ethmoidal artery is an important source of blood supply for various structures in the head, especially those related to respiration and olfaction. It also contributes to anastomoses between different arterial systems in this region.

The anterior ethmoidal artery can be injured by trauma or surgery involving the orbit, ethmoid bone, or nasal cavity. This can result in bleeding, infection, or ischemia of the tissues supplied by this artery. For example, damage to this artery can cause epistaxis (nosebleed), frontal sinusitis (inflammation of the frontal sinus), or anosmia (loss of smell).

The posterior ethmoidal artery is another branch of the ophthalmic artery that arises in the orbit and exits through the posterior ethmoidal foramen. It supplies blood to the posterior ethmoidal air cells, the dura mater, and the upper part of the nasal cavity.

The posterior ethmoidal artery originates from the ophthalmic artery after the anterior ethmoidal artery. It is smaller than the anterior ethmoidal artery and runs more posteriorly in the orbit. It travels with the posterior ethmoidal nerve, which is also a branch of the nasociliary nerve. The artery and nerve exit the orbit through the posterior ethmoidal foramen, which is an opening in the medial wall of the orbit near the sphenoid bone.

After leaving the orbit, the posterior ethmoidal artery enters the posterior ethmoidal canal, which is a bony passage within the ethmoid bone. The artery gives off branches that supply the posterior ethmoidal air cells. The artery then enters the anterior cranial fossa, where it divides into a meningeal branch and a nasal branch.

The meningeal branch of the posterior ethmoidal artery ascends to supply some of the dura mater of the anterior cranial fossa. It anastomoses with the meningeal branch of the anterior ethmoidal artery along the falx cerebri.

The nasal branch of the posterior ethmoidal artery descends through the cribriform plate of the ethmoid bone to enter the nasal cavity. It runs along the roof of the nasal cavity and splits into a medial and a lateral branch. The medial branch supplies blood to the upper part of the nasal septum, while the lateral branch supplies blood to the upper part of the lateral wall of the nasal cavity. The nasal branches form anastomoses with the sphenopalatine artery.

The posterior ethmoidal artery is an important source of blood supply for various structures in the head, especially those related to olfaction. It also contributes to anastomoses between different arterial systems in this region.

The posterior ethmoidal artery can be injured by trauma or surgery involving the orbit, ethmoid bone, or nasal cavity. This can result in bleeding, infection, or ischemia of the tissues supplied by this artery. For example, damage to this artery can cause epistaxis (nosebleed), posterior ethmoiditis (inflammation of the posterior ethmoid air cells), or anosmia (loss of smell).