Structure and Contents of the Orbit - The orbit is the cavity or socket of the skull that contains the eye and its appendages. - The volume of the orbit in adult humans is 30 millilitres, with the eye occupying 6.5ml. - The orbital contents include the eye, extraocular muscles, cranial nerves II, III, IV, V, and VI, blood vessels, fat, lacrimal gland, eyelids, and ligaments. - The orbit consists of a base, an apex, and four walls. - The walls of the orbit are formed by seven bones, including the frontal, lacrimal, ethmoid, zygomatic, maxillary, palatine, and sphenoid bones.

Openings in the Orbit - Important openings in the orbit include the supraorbital foramen, infraorbital foramen, superior orbital fissure, inferior orbital fissure, and optic canal. - These openings contain structures crucial to normal eye functioning, such as nerves and blood vessels. - The supraorbital foramen contains the supraorbital nerve, while the infraorbital foramen contains the infraorbital nerve. - The optic canal contains cranial nerve II (optic nerve) and the ophthalmic artery. - The superior orbital fissure is a pathway for intracranial communication and contains cranial nerves III, IV, VI, and ophthalmic branches of cranial nerve V.

Bony Walls of the Orbit - The orbit is formed by a mosaic of seven embryologically distinct bones, including the zygomatic, sphenoid, maxillary, lacrimal, ethmoid, frontal, and palatine bones. - The ethmoid bone forms the thinnest wall of the orbit, known as the lamina papyracea. - The frontal bone forms the superior margin of the orbital rim. - The orbital plate of the frontal bone and the lesser wing of the sphenoid form the roof of the orbit. - The floor of the orbit is formed by the maxilla, zygomatic bone, and palatine bone.

Borders of the Orbit - The base of the orbit, also known as the orbital margin, has four borders formed by different bones. - The superior margin is formed by the frontal bone. - The inferior margin is formed by the maxilla and zygomatic bone. - The medial margin is formed by the frontal bone and maxilla. - The lateral margin is formed by the zygomatic bone and frontal bone.

Function of the Orbit - The main function of the orbit is to hold and protect the eyes. - Eye movement is controlled by six extraocular muscles. - The ophthalmic artery and superior ophthalmic vein are important blood vessels in the orbit. - The optic canal contains the optic nerve, which is crucial for vision. - The orbit also protects the eyes from mechanical injury.