L15: Orbit Flashcards
What is the lining of the orbit called? What is this continuous with?
- Periorbita (same as periosteum) - Continuous with dura at optic canal and periosteum outside orbit
Bones of orbit?
- Mnemonic: Many Friendly Zebras Enjoy Lazy Picnics - Maxillary, Frontal, Zygomatic, Ethmoid, Lacrimal, Palatine
Walls of orbit?
- Medial wall - Lateral wall - Superior wall (aka roof) - Floor - Apex
Which wall of the orbit is the thickest and strongest? Thinnest and least strong?
- Thickest/strongest: lateral wall - Thinnest/frail: medial and inferior walls
Where is the apex of the orbit located?
- Optic canal in lesser wing of sphenoid bone
What is exophthalmos?
- Protrusion of eyeball
What are the tarsal plates and glands of the eye?
- Tarsal plates: CT that form skeleton of the lids - Tarsal glands: embedded in tarsal plate, secrete lipid material to lubricate edges of lids
What glands are found in the eyelids?
- Ciliary glands: sebaceous glands - Tarsal glands (in tarsal plates): lipid secreting glands to lubricate edges of lids
Which muscle elevates the upper eyelid? Innervation?
- Levator palpebrae superioris, by CN III
Components of lacrimal apparatus? Location and Function?
- Lacrimal glands/ducts: in lacrimal fossa (superolateral part of orbit), secretes lacrimal fluid - Lacrimal lake: collecting area of tears at medial angle of eye - Lacrimal canaliculi: lateral opening = lacrimal papillae, conveys tears from lacrimal lake to sac - Lacrimal sac: dilated upper end of the nasolacrimal duct, canaliculi open here - Nasolacrimal duct: extends inferiorly into nose, opens at inferior meatus of nasal cavity
Innervation of lacrimal gland?
- PSNS fibers carried in greater petrosal nerve of CN VII to pterygopalatine
Two conjunctiva of eye?
- Palpebral conjunctiva (covering of eyelid) - Bulbar conjunctiva (covering of eyeball)
Extraocular muscles? Innervation?
- SO4 LR6 rest III
Action of extraocular muscles?
- Superior rectus: rotate superiorly and medially - Medial rectus: rotate medially - Lateral rectus: rotate laterally - Inferior rectus: rotate inferiorly and medially - Superior oblique: abducts, depresses and rotates laterally - Inferior oblique: abducts, elevates and rotates laterally - Levator palpebrae: elevates superior eyelid
Branches of frontal nerve?
- Supraorbital - Supratrochlear
Branches of nasociliary nerve?
- Posterior ethmoidal - Anterior ethmoidal - Infratrochlear
Nerves that run through superior orbital fissure?
- CN V1 - CN III - CN IV - CN VI
Describe autonomic innervation to eye
1.) PSNS - PreG fibers for SM of eye travel with CN III - In orbit, preG fibers branch off CN III and enter into ciliary ganglion, located in orbit along posterolateral side of optic nerve - PostG fibers leave ganglion via short ciliary nerves (branches of CN V1) and enter eyeball, innervating SM of eyeball - Lacrimal gland: supplied by PSNS fibers from greater petrosal (preG fibers) of CN VII. Post G fibers originate from pterygopalatine ganglion and enter orbit via zygomatic branch of maxillary nerve (CN V2) 2.) SNS - PostG sympathetic fibers from sup cervical ganglion enter orbit with wall of blood vessels to eye
What blood vessels supply orbit?
- Opthalmic artery (branch off int carotid) enters through optic canal and gives rise to supraorbital, supratrochlear, lacrimal and central artery of retina - Superior and inferior ophthalmic veins drain the eye through the superior orbital fissure and enter cavernous sinus inside the skull
What supplies sensory innervation to eyeball?
- Nasociliary
What supplies sensory innervation to superior eyelid?
- Frontal, lacrimal
What supplies sensory to conjunctiva?
- Lacrimal
What bones form the superior wall of orbit?
- Frontal, sphenoid (lesser wing)
What bones form the medial wall of orbit?
- Ethmoid, frontal, lacrimal and sphenoid
What bones form floor/inferior wall of orbit?
- Maxilla, zygomatic, palatine
What bones form lateral wall of orbit
- sphenoid (greater wing), zygomatic
PSNS fibers destined for lacrimal gland innervation enter orbit via branches of what CN?
- CN V
Do all extraocular muscles attach to sclera of eyeball?
- False. All four recti muscles attach to sclera of eyeball and originate from common tendinous ring, which is a fibrous structure that surrounds optic foramen and part of superior orbital fissure
Long and short ciliary nerves are branches from what CN?
- Opthalmic division of CN V
Ptosis of the upper eyelid is produced by malfunction of what CN?
- CN III
Someone presents to your clinic with ptosis of left eye, inferior lateral rotation of eye and dilated pupil. Explain what the problem is?
- Ptosis is result of loss of function of levator palpebrae superioris - Dilation is seen in SNS, so if SNS is dominating with output causing this, then PSNS innervation to intraocular eye muscles are lost. - Inferior lateral rotation of eye (down and out): MR, IR, SR, IO have lost their function. Lateral rectus and superior oblique still function, causing this movement. - All of these functions are contained within CN III – this is oculomotor palsy.
