ORBIT
- The orbits are 4-sided pyramidal spaces on either side of the root of the nose.
- Each orbit has:
- Apex: is directed backwards.
- Base: it is the orbital opening on face.
- Four walls: roof, floor. Medial wall, and lateral wall. The medial walls of both orbits are parallel to each other, while the lateral walls are set at right angle to each others.
Openings in the orbit
1. Superior orbital fissure:
- it lies at the junction between the roof and the lateral wall of the bony orbit. It allows passage of structures between the middle cranial fossa and the orbit. The common tendinous ring of the extra-ocular muscles divides it into 3 parts.
✓Structures passing through it: lacrimal, frontal, trochlear, superior division of oculomotor, naso-ciliary, inferior division of oculomotor, and abducent nerves. In addition to the superior ophthalmic vein.
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N.B:
- Divisions of oculomotor nerve, naso-ciliary nerve, and abducent nerve pass through the superior orbital fissure (within the common tendinous ring).
2. Inferior orbital fissure:
- It lies between the floor and the lateral wall of the bony orbit. It allows communication between the orbit and temporal fossa (anteriorly), infratemporal fossa (in the middle), and pterygopalatine fossa (posteriorly).
✓Structures passing through it: the continuation of maxillary nerve, zygomatic nerve, infraorbital vessels, and communication between inferior ophthalmic vein and pterygoid venous plexus.
3. Optic canal:
- It represents the apex of the bony orbit, connecting the orbit to the middle cranial fossa.
✓Structures passing through it: optic nerve and ophthalmic artery.
← (III, IV, VI & V₁) Superior orbital fissure
- lacrimal
- frontal
- naso-ciliary