eye and orbital anatomy Flashcards
frontalis action
moves scalp and raises eyebrow
what nerve innervates frontal
CN 7
corrugator action
pulls medial eyebrow inf. and med. (forms 11s)
what nerve innervates corrugator
CN 7
procurus action
pulls forehead & eyebrow inf. - forms “bunny lines”
what innervates the procures muscle
CN 7
forehead and brow muscles
fantails, corrugator, procerus
eyelid muscles
levator, obricularis
action levator
elevates the eyelid
innervation of levator
CN 3
action of orbicularis
closes the eyelid
innervation of orbicularis
CN 7
periosteum anteriorly
fuses with septum at Marcus marginalus; septum important to prevent spread of infection into posterior orbit
periosteum posteriorly
fuses with dura of ON
where is the periosteum attached
firmly at orbital and suture lines
extra ocular muscles
superior rectus inferior rectus medial rectus lateral rectus superior oblique inferior oblique
superior rectus - action & innervation
elevates; CN 3
inferior rectus - action and innervation
depress; CN 3
medial rectus - action and innervation
adduct; CN 3
lateral rectus - action and innervation
abduct; CB 6
superior oblique - action and innervation
intort; CN 4
inferior oblique - action and innervation
extort; CN 3
what allows for slack of optic nerve in orbit
distance from globe to optic foramen (18 mm)
what is a sign of brain aneurysm
palsy of CN3
what cranial nerve is responsible for pupillary light reflex
CN 3 - oculomotor nerve
what does the oculomotor nerve innervate
medial rectus, superior rectus, inferior rectus, inferior oblique, levator palpebrae
what does the trochlear nerve innervate
superior oblique
what is the easiest cranial nerve to damage in head trauma
trochlear nerve (CN 4)
palsy of CN 4
causes head tilt
CN 5
trigeminal nerve
V1
ophthalmic branch
what can V1 be affected by
Zoster
what branches are part of V1
lacrimal branch, frontal branch, nasocilliary branch
sensation to the cornea
V1: ophthalmic branch
CN6
abducens nerve
abducens nerve innervates
lateral rectus
palsy of CN6
common in small strokes
cause of double vision
CN 6
easily affected by intracranial pressure
CN6 because it does not travel the wall of the cavernous sinus so easily affected by increased intracranial pressure
CN 7
facial nerve
CN 7 innervates
muscles of facial expression
CN 7 stimulates ____
tear production
Bell’s palsy
see difficulty with eyelid closure due to obicularis occuli paralysis
annulus of zinn
four rectus muscles originate from a ring of fibrous tissue attached to the posterior orbit
which nerves enter the orbit within the annulus of zinn
optic nerve (CNII), the superior and inferior divisions of the oculomotor nerve (CN III), the abducens nerve (CN VI), and the nasociliary branch of the ophthalmic branch of the trigeminal nerve (CN V1)
what does not pass through the annulus of zinn
trochlear nerve and the frontal and lacrimal branches of the ophthalmic branch of the trigemnical nerve (CN V1) do not pass through the annulus of Zinn
lateral wall
thickest and strongest wall; rarely affect in trauma
medial wall
thinnest; level of cribriform plate; floor of anterior cranial fossa; anterior and posterior ethmoidal arteries; lamina papyracea
lamina papyracea
thinnest bone; often fractures; can be site of cellulitis extension
superior orbital fissure nerves
lacrimal n (V1) frontal n (V1) trochlear nerve (CN4) sup div of CN3 nasociliary N (V1) abducens N (CN6) inf. div of CN3
Lazy French Tarts Sit Naked and Inviting
ophthalmic artery
a branch of the internal carotid artery, enters the orbit through the optic canal then travels along the medial wall of the orbit
first branch of ophthalmic artery
central retinal artery; penetrate the optic nerve and enters the eye through the center of the nerve
superior and inferior ophthalmic veins
drain the orbit
branches of the superior and inferior ophthalmic veins
exit through the superior and inferior orbital fissures before draining into the cavernous sinus
puncta
where tears exit the ye
canaliculus
pipe that leads to lacrimal sac
lacrimal sac
tear reservoir - often site of infection if outflow is blocked
nasolacrimal duct
outflow into the nose for tears
