The orbit is a paired pyramid-shaped bony cavity located in the skull on either side of the root of the nose. The orbit houses and protects the eye and its accessory structures.

Seven bones that contribute to the formation of the orbit are listed below:

Anteriorly, each orbit opens onto the face with an approximately quadrangular-shaped orbital opening (orbital rim).

This opening has four margins - supraorbital, infraorbital, medial, and lateral orbital margins.

Walls

The orbit has four walls:

Openings

The walls of the orbit contain the following openings:

Optic canal - connects the orbit with the middle cranial fossa; transmits the optic nerve (CN II) and ophthalmic artery;
Superior orbital fissure - connects the orbit with the middle cranial fossa; transmits the oculomotor (CN III), trochlear (CN IV), ophthalmic (CN V1), and abducens (CN VI) nerves, ophthalmic veins, and sympathetic nerve fibers;
Anterior ethmoidal foramen - connects the orbit with the anterior cranial fossa, transmits the anterior ethmoidal nerve and blood vessels;
Posterior ethmoidal foramen - connects the nasal cavity and posterior ethmoidal air cells with the orbit; transmits the posterior ethmoidal nerve and blood vessels;
Nasolacrimal canal - connects the nasal cavity (inferior nasal meatus) with the orbit; it carries and drains lacrimal secretions from the eyes;
Infraorbital canal - connects the orbit with the infraorbital foramen located on the anterior surface of the maxilla; transmits the infraorbital artery, vein, and nerve (the maxillary division of the trigeminal nerve (CN V2));
Inferior orbital fissure - connects the orbit with the pterygopalatine and infratemporal fossae; transmits zygomatic nerve (from the maxillary division of the trigeminal nerve (CN V2), branch of the inferior ophthalmic vein, infraorbital artery (from the maxillary artery) and vein; ascending branches of the pterygopalatine ganglion.

To learn more about this topic, check out our study unit devoted to the orbit!

Unlock with Premium

Orbit