Bony Orbit

 🦴 Bony Orbit: Overview

• Shape: Pyramidal, with the base facing anteriorly and the apex pointing posteriorly

• Contents:

• Eyeball (globe)

• Extraocular muscles

• Optic nerve

• Lacrimal gland

• Fat

• Vessels and nerves

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🧱 Bones of the Orbit (7 in Total)

👉 Mnemonic: "My Sister Likes Eating Zucchini Pasta Freshly"

Bone	Location in Orbit
Maxilla	Floor (medial part)
Sphenoid	Posterior wall (roof & lateral)
Lacrimal	Medial wall
Ethmoid	Medial wall
Zygomatic	Lateral wall & floor
Palatine (orbital process)	Tiny part of floor (posteriorly)
Frontal	Roof of orbit

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📐 Walls of the Orbit

1. Roof (Superior Wall)

• Formed by: Frontal bone and lesser wing of sphenoid

• Related to: Frontal sinus, anterior cranial fossa

• Contains: Lacrimal fossa (for lacrimal gland)

2. Floor (Inferior Wall)

• Formed by: Maxilla, zygomatic, and palatine bones

• Related to: Maxillary sinus

• Contains: Inferior orbital fissure

3. Medial Wall

• Formed by: Ethmoid, lacrimal, maxilla, and sphenoid

• Thinnest wall (lamina papyracea of ethmoid)

• Contains: Lacrimal fossa and nasolacrimal canal

4. Lateral Wall

• Formed by: Zygomatic and greater wing of sphenoid

• Thickest wall (protects eye from trauma)

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🕳️ Key Openings in the Orbit

Opening	Location	Transmits
Optic canal	Apex, sphenoid bone	CN II (optic nerve), ophthalmic artery
Superior orbital fissure	Between sphenoid wings	CN III, IV, V₁, VI, superior ophthalmic vein
Inferior orbital fissure	Floor (between maxilla & sphenoid)	Infraorbital nerve & vessels, zygomatic nerve
Nasolacrimal canal	Medial wall to nasal cavity	Nasolacrimal duct

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🔍 Clinical Relevance

• Orbital blowout fracture:

  • Often affects floor (maxilla) or medial wall

  • Can trap inferior rectus muscle, causing diplopia (esp. when looking up)

• Orbital cellulitis:

  • Infection of orbital tissues—may spread from ethmoid sinus

• Optic nerve compression:

  • Can occur with trauma or tumors in the optic canal

• Enophthalmos / Exophthalmos:

  • Sunken/protruding eye due to volume changes in orbital contents

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🧠 Bonus Tip: Orbit vs. Eye Socket

• The orbit = bony cavity housing the entire eye apparatus

• The eye socket = informal term often used synonymously with the orbit