Inferior orbital fissure
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The inferior orbital fissure (IOF) lies in the floor of the orbit inferior to the superior orbital fissure and it is bounded superiorly by the greater wing of sphenoid, inferiorly by maxilla and orbital process of palatine bone and laterally by the zygomatic bone. It opens into posterolateral aspect of orbital floor. It joins medially with the pterygomaxillary fissure at a right angle.
It transmits the:
- infra-orbital nerve (from the maxillary division of trigeminal nerve)
- zygomatic nerve (from the maxillary division of trigeminal nerve)
- a branch of the inferior ophthalmic vein and several emissary veins connecting it to the pterygoid venous plexus
- infra-orbital artery (from the maxillary artery) and vein
- orbital ganglionic branches of the pterygopalatine ganglion from the maxillary division of the trigeminal nerve
The contents, and their ordering, may be remembered using this mnemonic.
The orbitalis muscle 2 is a small vestigial smooth muscle that may cover part of the fissure of the infra-orbital groove where it blends in with the periosteum. It is of unknown significance in humans, but in some animals may help control the volume of the orbit and aid in autonomic regulation of orbital blood vessels.