[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Ophthalmology](https://durgical.com/en/ophthalmology/) › [Clinical anatomy and physiology](https://durgical.com/en/ophthalmology/areas/anatomy-physiology/) › The orbit, orbital septum and eyelids # The orbit, orbital septum and eyelids - Anatomy and physiology The orbit is a bony cone with thin walls next to the sinuses. The orbital septum separates lid infections from orbital ones; the lids protect the eye. Updated Nov 5, 2026 **See it in 3D:** [Eyelids](https://durgical.com/en/anatomy/superior-tarsus/) · [Levator palpebrae](https://durgical.com/en/anatomy/levator-palpebrae-superioris/) · [Orbicularis oculi](https://durgical.com/en/anatomy/orbital-part-of-orbicularis-oculi/) · [Optic canal](https://durgical.com/en/anatomy/optic-canal/) · [Superior orbital fissure](https://durgical.com/en/anatomy/superior-orbital-fissure/) ## Key points - Thinnest walls: medial (ethmoid) and floor (maxilla). - Orbital septum: preseptal vs orbital cellulitis. - Superior orbital fissure: III, IV, V1, VI. - Müller muscle (sympathetic): mild ptosis in Horner. ## What it is The orbit is a cone of seven bones that holds the eye, its muscles, nerves, vessels, fat and lacrimal gland. Its medial wall and floor are thin and border the ethmoid and maxillary sinuses. At the apex, nerves and vessels enter through the optic canal and the superior orbital fissure. In front, the orbital septum, a fibrous sheet from the orbital rim to the lids, divides preseptal tissues from the orbit proper. ## Clinical anatomy - Bones: frontal, zygomatic, maxilla, ethmoid, sphenoid, lacrimal and palatine. - Medial wall (lamina papyracea of the ethmoid) and floor (maxilla): the thinnest walls. - Optic canal: optic nerve and ophthalmic artery; superior orbital fissure: nerves III, IV, VI, the ophthalmic division of V and the superior ophthalmic vein. - Eyelid layers: skin and orbicularis oculi (facial nerve) in front; tarsal plate and conjunctiva behind. - Upper lid elevators: levator palpebrae (oculomotor nerve) and the small Müller muscle (sympathetic). ## Physiology - The orbit protects the eye and lets it rotate freely on a cushion of fat. - The lids close (orbicularis, facial nerve), spread tears and shield the cornea. - Orbital veins have no valves and drain to the cavernous sinus. ## Clinical correlation - Ethmoid sinusitis spreads through the thin medial wall: orbital cellulitis in children. - A blow to the orbit can fracture the floor: numb cheek (infraorbital nerve), restricted upgaze and sunken eye. - Infections in front of the septum (preseptal) are milder than those behind it (orbital). - Horner syndrome gives mild ptosis (Müller muscle); third nerve palsy gives marked ptosis (levator); facial palsy prevents closure. - Valveless veins let infection from the face spread to the cavernous sinus. ## Next step / Initial management - Lid swelling with normal vision and movements: preseptal cellulitis, oral antibiotics and review in 24 to 48 hours. - Proptosis, painful movements or reduced vision: orbital cellulitis, admission and CT. - Orbital trauma with numb cheek or restricted upgaze: CT of the orbits; urgent in children with nausea or slow pulse. - Facial palsy with incomplete closure: lubricants and cornea protection, refer if the cornea stains. ## Test yourself Think of the answer, then tap the question to see it. ## Through which wall does ethmoid sinusitis reach the orbit? The thin medial wall, the lamina papyracea of the ethmoid bone. ## Which structures pass through the superior orbital fissure? The oculomotor, trochlear and abducens nerves, the ophthalmic division of the trigeminal nerve and the superior ophthalmic vein. ## Why is ptosis mild in Horner syndrome? Because only the small sympathetic Müller muscle is weak; the levator still works. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/ophthalmology/the-orbit-orbital-septum-and-eyelids/) ## Elsewhere in DurgiPedia - [Conjunctiva, eyelid glands and lacrimal gland](https://durgical.com/en/histology/conjunctiva-eyelid-glands-and-lacrimal-gland/) ## Connections ## See it in 3D 5 The structures of Durgical's 3D anatomy where it is found. - [Eyelids](https://durgical.com/en/anatomy/superior-tarsus/) - [Levator palpebrae](https://durgical.com/en/anatomy/levator-palpebrae-superioris/) - [Orbicularis oculi](https://durgical.com/en/anatomy/orbital-part-of-orbicularis-oculi/) - [Optic canal](https://durgical.com/en/anatomy/optic-canal/) - [Superior orbital fissure](https://durgical.com/en/anatomy/superior-orbital-fissure/) ## Related 5 - [Proptosis and periorbital swelling](https://durgical.com/en/ophthalmology/proptosis-and-periorbital-swelling/) - [Drooping eyelid (ptosis)](https://durgical.com/en/ophthalmology/drooping-eyelid/) - [Extraocular muscles and the cardinal positions of gaze](https://durgical.com/en/ophthalmology/extraocular-muscles-and-the-cardinal-positions-of-gaze/) - [Eyelid lacerations: which to refer](https://durgical.com/en/ophthalmology/eyelid-lacerations-which-to-refer/) - [Orbital compartment syndrome and lateral canthotomy](https://durgical.com/en/ophthalmology/orbital-compartment-syndrome-and-lateral-canthotomy/) ## Related conditions 4 - [Orbital cellulitis](https://durgical.com/en/conditions/orbital-cellulitis/) - [Orbital floor (blowout) fracture](https://durgical.com/en/conditions/orbital-floor-fracture/) - [Horner syndrome](https://durgical.com/en/conditions/horner-syndrome/) - [Bell palsy](https://durgical.com/en/conditions/bell-palsy/) [← All of ophthalmology](https://durgical.com/en/ophthalmology/) Educational content; not a clinical guideline and no substitute for assessment by a health professional. For sudden visual loss, severe eye pain, a chemical burn or an eye injury, go to an emergency department at once. Sources: [Anatomy, Head and Neck, Orbit](https://www.ncbi.nlm.nih.gov/books/NBK539843/) (StatPearls Publishing (NCBI Bookshelf), 2023); [Anatomy, Head and Neck: Eyelid](https://www.ncbi.nlm.nih.gov/books/NBK482304/) (StatPearls Publishing (NCBI Bookshelf), 2023); [Anatomy, Head and Neck: Eye, Superior Tarsal Muscle (Müller Muscle)](https://www.ncbi.nlm.nih.gov/books/NBK540964/) (StatPearls Publishing (NCBI Bookshelf), 2024). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/ophthalmology/the-orbit-orbital-septum-and-eyelids/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/ophthalmology/the-orbit-orbital-septum-and-eyelids/