021 the orbit and its contents Flashcards
what bones make up the orbit?
- frontal
- zygomatic
- maxilla
- lacrimal
- ethmoid
-sphenoid
describe the position of the eye in the orbit
- medial orbital wall lies parallel to the midsagittal plane
- the lateral wall of the orbit is angled with regards to the midsagittal plane
- the orbital axis and visual axis of the eye do not overlap = consequences on how the eye muscles work
- the orbital axis = dead between lateral and medial orbit wall plane
- visual axis = parallel to midsagittal plane (looking straight ahead
what happens when the zygomatic bone is fractured?
- makes up part of orbit, so if it is fractured, the eye will be out of place
- can cause diplopia (double vision)
- suspensory ligaments of the eye in the horizontal plane become loose or rupture
- extra-ocular muscles can become obstructed or trapped, thus restricting eye movement/field of vision
what is a blowout fracture and what is its clinical significance?
- when trauma/force causes fraction of the middle inferior bones, mostly ethmoid or maxillary
- common symptoms = diplopia (double vision), sunken eye, loss of sensation of cheek, and upper gums due to infraorbital injury of CNVii
what are the 7 extraocular eye muscles?
- levator palpebrae
- superior tarsal
- superior oblique
- inferior oblique
- superior rectus
- inferior rectus
- medial rectus
- lateral rectus
what is the function of levator palpebrae and superior tarsal muscle?
- elevate/raise the upper eyelid
what is a?
superior oblique muscle
what is b?
trochlea
what is c?
superior oblique tendon
what is d?
superior rectus
what is e?
lateral rectus
what is f?
inferior oblique
what is g?
inferior rectus
what is h?
common tendinous ring
what is i?
medial rectus
what is the function of superior rectus?
moving the eye upwards
- also contributes to adduction and medial rotation of eyeball
what is the innervation of levator palpebrae?
oculomotor nerve
what is the innervation of superior tarsal muscle?
sympathetic
what is the innervation of superior rectus?
oculomotor nerve
what is the function of inferior rectus?
- moving the eye downwards
- also contributes to adduction and lateral rotation of eyeball
what is the innervation of inferior rectus?
oculomotor nerve
what is the function of medial rectus?
- adducts eye (moves medially)
what is the innervation of medial rectus?
oculomotor nerve
what is the function of lateral rectus?
- abducts eye (moves laterally)
what is the innervation of lateral rectus?
- abducens nerve
where do all the rectus eye muscles originate from?
common tendinous ring
what is the function of superior oblique muscle?
- move eye down and outwards (abducts)
- also medially rotates eye
what is the innervation of superior oblique muscle?
trochlear nerve
what is the function of inferior oblique muscle?
- moves eye up and out and laterally rotates eye
what is a?
- greater wing of sphenoid
what is b?
superior orbital fissure
what is c?
lesser wing of sphenoid
what is d?
frontal bone
what is e?
optic canal
what is f?
ethmoidal foramina
what is g?
ethmoid bone
what is h?
lacrimal groove
what is i?
lacrimal bone
what is j?
palatine bone
what is k?
maxilla
what is L?
inferior orbital fissure
what is m?
zygomatic bone
what is the function of orbicularis oculi?
- closes the eyelids
what is the orbicularis oculi innervated by?
facial nerve
what is the best way to test all the extraocular muscles?
- H test
- have the patient track an object in a H pattern without moving their head
what are the different canals, fissures and foramen in the orbit?
- optic canal
- superior orbital fissure
- inferior orbital fissure
- ethmoidal foramina
- nasolacrimal canal
what passes through the optic canal?
- optic nerve
- ophthalmic artery
what passes through the superior orbital fissure?
- oculomotor nerve (superior and inferior branches)
- trochlear nerve
- abducens nerve
- ophthalmic nerve branches ( lacrimal, frontal, nasociliary)
- superior ophthalmic vein
what passes through the inferior orbital fissure?
inferior ophthalmic vein
what is a?l
superior orbital fissure
what is b?
lacrimal nerve (branch of ophthalmic division CNVi)
what is c?
frontal nerve (branch of ophthalmic division CNVi)
what is d?
trochlear nerve
what is e?
superior rectus
what is f?
levator palpebrae
what is g?
optic nerve
what is h?
superior oblique
what is i?
ophthalmic artery
what is j?
medial rectus
what is k?
superior division of oculomotor nerve
what is L?
nasociliary nerve (branch of ophthalmic division (CNVi)
what is m?
abducent nerve
what is n?
inferior division of oculomotor nerve
what is o?
inferior rectus
what is p?
inferior ophthalmic vein
what is q?
inferior orbital fissure
what is r?
lateral rectus
describe the arterial supply to the orbit
- ophthalmic artery enters through optic canal
- then branches:
- central retinal artery (enters optic nerve, damage causes blindness)
- lacrimal artery = lateral to lacrimal gland, eye lids and conjunctiva
- posterior ciliary arteries = central into eye
- ethmoidal arteries = medial to ethmoidal air cells in nasal cavity
- supra-orbital, supratrochlear and nasal arteries = medial, supply nose and forehead
describe the venous drainage of the orbit
- superior: supra-orbital vein from forehead –> superior ophthalmic vein –> cavernous sinus
- inferior: angular vein from cheek –> infra-orbital/inferior ophthalmic veins –> pterygoid plexus/cavernous sinus
what is the clinical significance of the cavernous sinus?
- most facial veins drain into it
- easily get infections spread through it
- could spread to the brain
