PAIRED & UNPAIRED BONES

• The medial wall of the orbit is the thinnest of the orbital bones (2-4mm) and is quadrilateral in shape.
• The foramen rotundum transmits the maxillary nerve.
• The greater wings of sphenoid contain three important openings near their roots: Foramen rotundum, Foramen ovale, and Foramen spinosum.
• The pterygoid processes are extensions of the basal surface of the sphenoid body and border the frontal bone, parietal bone, squamous part of the temporal bone, and occipital bone.
• The greater wings of sphenoid arise posterolaterally from the body and form the infratemporal surfaces.
• The roof of the orbit is triangular in shape and formed by the frontal bone, lesser wing of sphenoid, and lacrimal fossa/ fossa for the lacrimal gland.
• The floor of the orbit is triangular in shape and it slopes downward and laterally, with a measurement of 47.6 mm, and is the shortest orbital boundary.
• The foramen ovale allows the passage of the Mandibular nerve, Accessory meningeal artery, Lesser petrosal nerve, and Emissary vein (mnemonic "MALE").
• The anterior surfaces of the greater wings make up part of the posterior aspect of the lateral wall of the orbit.
• The foramen spinosum is traversed by the middle meningeal vessels and the spinous nerve (branch of mandibular nerve) lies at the posterior margin of the greater wings.
• Orbit: Bony orbit; orbital cavity; space of compartment of head which is bound by the internal surface of the wall of orbit.
• Orbit contains the eye, anterior portion of the optic nerve, ocular muscles and ocular adnexa.
• Orbit is placed on the either side of the midsagittal plane of the skull between the cranium and the skeleton of the face.
• Orbit is shaped like a four sides pyramid with base at the anterior orbital margin and apex at the posterior margin (at the optic foramen).
• The anterior portion of the medial surface of the lacrimal bone forms part of the middle nasal meatus.
• The medial surface of the lacrimal bone faces the nasal cavity, also known as the nasal surface, and is notable for a longitudinal furrow corresponding to the posterior lacrimal crest of the orbital surface.
• The posterior border of the lacrimal bone articulates with the orbital lamina of the ethmoid bone.
• The palatine bone is a paired bone located between the maxillae and the pterygoid process of the sphenoid bone, and its function is to help in building the three cavities within the skull and articulating with five bones: maxilla, sphenoid, ethmoid, inferior nasal concha, and vomer.
• The anterior border of the lacrimal bone articulates with the frontal process of the maxilla.
• The inferior border of the lacrimal bone is divided into two parts by the inferior edge of the posterior lacrimal crest, with one part articulating with the orbital plate of the maxilla and the other part extending downward, called the Descending process, which articulates with the lacrimal process of the inferior nasal concha and participates in enclosing the bony canal for the nasolacrimal duct.
• The Posterior lacrimal crest divides the lateral surface of the bone into two portions: the Anterior portion related to the lacrimal sac and lacrimal canaliculi, and the Posterior portion which is a smooth surface that participates in forming the medial wall of the orbit.
• The lateral surface of the lacrimal bone also extends in the shape of a hook called the lacrimal hamulus and it articulates with the lacrimal tubercle of the maxilla, enclosing the lacrimal canaliculus.
• The superior border of the lacrimal bone articulates with the frontal bone.
• The posterior portion of the medial surface of the lacrimal bone articulates with the ethmoid bone, enclosing some ethmoidal air cells.
• The lateral surface of the lacrimal bone faces towards the contents of the orbit, also known as the orbital surface, and is notable for a vertical ridge called the Posterior lacrimal crest.
• Orbit is designed to support and provide protection to the orbital soft tissues.
• The lateral orbital tubercle is a small elevation on the orbital surface of the zygomatic bone just behind and within the orbital margin, 11 mm below the frontozygomatic suture, and serves as an attachment for the check ligament of the lateral rectus muscle, the lateral palpebral ligament, the suspensory ligament of Lockwood, and the levator palpebrae superioris muscle.
• The thickest and strongest wall of the orbit is formed by the orbital surface of the greater wing of the sphenoid (posterior) and the orbital surface of the zygomatic bone (anterior).
• The ophthalmic artery (arteria ophthalmica) is the major blood supply of the orbit.
• Orbit is intended essentially as a socket for the eyeball, containing the muscles, orbital fats, nerves, vessels proper to it.
• Orbit also transmits certain vessels and nerves to supply the areas of the orbital aperture.
• Plain Orbital Muscles are muscles in the orbit that covers and protects the whole eye from injury and trauma, acting as a caution to protect the orbital bone from fractures.
• The Medial Orbital Margin is not continuous due to the overlapping of the anterior and posterior lacrimal crests.
• The Frontal Bone also contains the Supraorbital Notch/ Foramen which transmits the supraorbital artery and nerve.
• The Frontal Bone forms the superior orbital margin, an easily palpable prominence, sharp in its lateral two thirds, located 25 mm from the midline and more rounded medially.
• Extrinsic eye muscles are also known as the “Levator Palpebrae Superioris (LPS)” muscle in the orbit that elevates the superior (upper) eyelid.
• The Medial Orbital Margin is formed by the anterior lacrimal crest on the frontal process of the maxilla and the posterior lacrimal crest on the lacrimal.
• The Zygomatic Bone forms the lateral orbital margin, the thickest among the margins but it is also the most exposed to injury.
• The Clinical Comment about the orbital margin is that it is relatively heavy construction makes it quite resistant to blunt trauma, but it can relatively be broken.
• The Bones of the Orbit include paired bones: Lacrimal, Palatine, Maxillary, and Zygomatic, and unpaired bones: Frontal, Ethmoid, Sphenoid (greater and lesser).