Orbit Flashcards
What are the 2 layers of the conjunctiva
palpebral and bulbar
Describe the palpebral conjunctiva
membrane of the inner eyelid
Describe the bulbar conjunctiva
membrane of the actual eyeball
What is the potential space called between the palpebral and bulbar conjunctiva?
conjunctival sac
Define the conjunctiva sac
The potential space between the palpebral conjunctiva and bulbar conjunctiva
Define the palpebral fissure
the slit between the 2 eyelids
The palpebral and bulbar conjunctiva are connected at the ___
fornices
What cranial nerves open/close the eye?
cn 3 = opens the eye
cn 7 = closes the eye
What are the 4 sets of ligaments/tendons that support the eyelid?
medial/lateral palpebral ligament
superior/inferior tarsus
tendon of levator palpebrae superioris m
orbital septum
Describe where the medial/lateral palpebral ligaments are found
they are found on medial/lateral commisures of the eyelid projecting laterally
Describe where the superior and inferior tarsus are found
They are an inner circle around the eyeball
Describe where the orbital septum is found
The orbital septum is found as an outer circle around the superior/inferior tarsus
Describe where the tendon of levator palpebrae superioris is found
projecting upwards from the upper palpebra
What travels through the optic canal?
CN 2 and opthalmic a
What travels through the superior orbital fissure
CN 3, 4, 6, V1, opthalmic vv
What travels through supra-orbital notch?
supra-orbital n and artery
What travels through inferior orbital fissure?
infra-orbital nerve and a
zygomatic n and a
What travels through infra-orbital formmen?
infra-orbital n and a
Infra-orbital nerve is a branch off of ____
CN V2
What travels through anterior./posterior ethmoidal foramen?
anterior/posterior ethmoidal n., a.
Anterior and posterior ethmoidal nerves are a branch off of ___
CN V1
What are the main structures found on the medial wall of the bony orbit?
anterior ethmoidal foramen posterior ethmoidal foramen optic canal superior orbital fissure inferior orbital fissure fossa of lacrimal sac
If you pierce the orbit’s roof, you enter ___
anterior cranial fossa (frontal lobe)
If you pierce the orbit’s floor, you enter ___
maxillary sinus
If you pierce the orbit’s medial wall, you enter ____
ethmoidal air cells
If you pierce the orbit’s lateral wall, you enter the ___
temporal fossa
If you pierce the orbit’s superior orbital fissure, you pierce the ____
middle cranial fossa
What are the 2 main portions of the OUTER eye?
cornea and sclera
T/F: Cornea and sclera are made up of the same molecular composition
True
If cornea and sclera are made up of the same molecular composition, why is the cornea transparent and the sclera is not?
cornea ECM proteins are all aligned parallel (think: light polarization)
sclera ECM proteins are not aligned parallel to e/o
Why is the sclera thick?
because it is the point of attachment for extraoccular muscles
What are the 4 components of the MIDDLE eye?
choroid
iris
pupil
ciliary body
What is the vascular later of the eye?
why?
middle eye = vascular layer
because CHOROID - ciliary aa and vorticose vv
Describe the choroid in the middle eye
thin layer of ciliary aa and vorticose vv
this is why the middle eye is high vascularized
Vorticose vv and ciliary aa are found in the ___ of the eye
choroid
middle eye
What part of middle eye is responsible for accomodation of the lens?
ciliary body (smooth muscles responsible for accomodation of the eye)
dilator pupillae m
sphincter pupillae m
Describe the difference in dilator pupillae and sphincter pupillae
dilator pupillae = radiating spokes
sphincter pupillae = circular around pupil
How do dilator pupillae m and sphincter pupillae m connect to the lens?
zonular ligaments
Zonular ligaments connect __ to __
ciliary body mm to the lens
for accomodation
What is the iris?
colored smooth muscle behind the cornea that controls pupil size
What is the colored smooth muscle of the eye?
the iris
What is the pupil?
adjustable aperture through which light enters
Which part of the middle eye is adjustable aperture through which light enters
the pupil
What are the 4 components of the inner eye?
retina
macula lutea
fovea centralis
optic disc
Describe the retinas
neural layer which receives light rays and converts it into a neural stimulus
Describe the macula lutea
Part of the retina
OVAL region for visual acuity
Macula lutea is visible on the retina because it is ___
oval shaped
has a dip inwards on the retina
(macula lutea is for visual acuity)
What is the fovea centralis?
fovea centralis is the highest level of visual acuity (most accurate) on the retina
it is part of the macula lutea
What is the optic disc?
the part of the inner eye where CN 2 and retinal vessels enter/exit
What enters/exits at the optic disc?
CN 2 and retinal vessels
Dilator pupillae m. / Sphincter pupillae m.
Which is sympathetic/parasympathetic?
sphincter pupillae - parasympathetic
dilator pupillae - sympathetic innervation
sympathetics of dilator pupillae come from ___
internal carotid plexus
parasympathetics of sphincter pupillae come from ___
ciliary ganglion
What 4 components of the eye play a part in refraction?
1 cornea
2 lens
3 acqueous humor
4 vitreous humor (body)
Most refraction in the eye takes place in the ___
cornea
___ focuses light rays for near/distant objects on the retina (plays role in refraction)
lens
What liquid is between the cornea and the lens?
acqeous humor
What liquid is between the lens and the retina?
vitreous humor (body)
The anterior and posterior chambers are where?
PART OF ACQEOUS HUMOR
anterior chamber - bw cornea and iris
posterior chamber - bw iris and ciliary body
Describe the composition of aqeous humor vs vitreous humor?
aqueous humor - watery anterior to lens
vitreous humor (body) - gelatinous posterior to lens
Watery aqueous humor travels in which direction through the chambers?
How does it go backwards?
travels posterior to anterior
travels anterior to posterior through canal of schlemm (blockage = glaucoma)
What are the 4 components of the lacrimal apparatus?
1 lacrimal gland
2 lacrimal canaliculi
3 lacrimal sac
4 nasolacrimal duct
Where on the eye is the lacrimal gland found?
superolaterally
What are the parts of the lacrimal gland?
orbital part
palpebral part
Lacrimal gland produces ___.
What are these for? How do they travel?
lacrimal fluid (tears)
used for lubrication
travel inferomedially
Describe lacrimal canaliculi
What are the parts?
superior and inferior lacrimal canaliculi (separate parts)
openings of canaliculi: PUNCTA
transports tears from canaliculi -> lacrimal lake -> lacrimal sac
Lacrimal canaliculi transport lacrimal fluid from to __
lacrimal sac
What are the puncta? Where are they found?
puncta are the openings of the lacrimal canaliculi
transport tears from lacrimal lake -> lacrimal sac
The lacrimal sac drains tears into ___
nasolacrimal duct
Nasolacrimal duct drains tears into ___
nasolacrimal canal (opens underneath the inferior nasal conchae)
The nasolacrimal canal is located ___
underneath the inferior nasal conchae
Name all of the extra-ocular mms
levator palpebrae superioris m superior rectus m inferior rectus m lateral rectus m medial rectus m superior oblique m inferior oblique m
All extraocular muscles except for ____ insert onto the ___
all extraocular muscles except for levator palpebrae superioris insert onto the sclera of the eye
Action of levator palpebrae superioris m
raises upper eyelid
Action of superior rectus muscle
elevates/adducts the eye
Action of inferior rectus muscle
depresses/adducts the eye
Action of lateral rectus muscle
abducts eye
Action of medial rectus muscle
adducts eye
Action of superior oblique muscle
depress, abduct, medially rotate eye
Action of inferior oblique muscle
elevate, abduct, laterally rotate eye
What is the formula for motor innervation of extraocular mm
LR6(SO4)R3
CN 3 innervates which extraocular mm
levator palpebrae superioris superior rectus inferior rectus middle rectus inferior oblique
CN 6 innervates which extraoccular mm
lateral rectus
CN 4 innervates which extraoccular mm
superior oblique m
CN 3 innervates most of the extraoccular mm, and WHAT ELSE
provides parasympathetics to ciliary gangion
Why do we test each extraocular mm individually?
to see if the damage is to a single CN or a single muscle
If the eye is in NEUTRAL position, we are testing ___ mm
lateral rectus and medial rectus
If the eye is ABDUCTING, we are testing ____ mm
superior and inferior rectus mm
If the eye is ADDUCTING, we are testing ____ mm
superior and inferior oblique mm
Nerve fibers of the optic nerve run between __ and __
eye and optic chiasm
Nerve fibers of the optic chiasm are found where
in the X shaped portion of the anterior cranial vault, intermingling of fibers
Nerve fibers of the optic tract are found between __ and __
optic chiasm and brain
temporal and nasal visual fields:
which cross and which remain ipsilateral?
nasal visual fields remain ipsilateral
temporal visual fields cross at optic chiasm
A lesion at the optic nerve leads to __
total blindness of that eye
A lesion at the optic chiasm leads to ___
peripheral blindness
A lesion at the optic tract leads to ___
ipsilateral nasal vision lost
contralateral temporal vision lost
Ciliary ganglion receives 3 types of fibers. what are they?
sensory fibers
pre-synaptic parasympathetic fibers
post-synaptic sympathetic fibers
the sensory fibers going into ciliary ganglion come from what root?
nasociliary root
the pre-synaptic parasympathetic fibers going into ciliary ganglion come from ___ via what root?
CN 3 via parsympathetic (occulomotor) root
the post-synaptic sympathetic fibers going into ciliary gangion come from ___ via what root?
internal carotid plexus via sympathetic root
The sympathetic fibers going into ciliary ganglion are post-sympathetic. why?
because sympathetic!
has already synapsed in superior cervical ganglion!
The pupillary light reflex tests which CN ?
2 and 3
During pupillary light reflex, if an eye remains dilated, this shows there is a lesion ___
in CN 3 parasympathetic pathway
What are the main 7 arteries of the eye/orbit?
opthalmic a posterior ciliary aa central retina aa ethmoida aa supraorbital a supratrochlear a lacrimal a
Which artery gives rise to all aa of the eye?
opthalmic a
Posterior ciliary aa supplies ___
outer/middle layers of the eye
Central retinal aa supplies __
inner retinal layer of the eye
Ethmoidal aa supplies __
anterior cranial fossa, sinuses, nose
Supraorbital a supplies ___
central forehead
Supratrochlear a supplies ___
medial forehead
Lacrimal a supplies ___
lacrimal gland
What are the 3 main divisions of V1 in the orbit?
NFL:
nasociliary nerve
frontal nerve
lacrimal nerve
What are the branches of nasociliary nerve?
ethmoidal nerve
infratrochelear nerve
long ciliary nerve
Which nerve provides sympathetics and sensory innervation to posterior eye?
long ciliary nerve (branch off of nasociliary nerve, first division of CN V1)
What are the branches of frontal nerve?
supra-orbital nerve
supra-trochlear nerve
What does lacrimal nerve supply?
lacrimal gland and conjunctiva
What are the 2 main veins of the ORBIT?
superior opthalmic vein
inferior opthalmic vein
superior opthalmic vein and inferior opthalmic vein join with facial vein to drain into ___
cavernous sinus
AFTER JOINING WITH FACIAL VEIN
superior opthalmic vein and inferior opthalmic vein join with ____ to drain into cavernous sinus
facial vein
What are the 2 main veins of the EYEBALL
central retinal vein
vorticose vein
What does central retinal vein drain?
What does it drain into?
drains retina
drains into cavernous sinus
What does vorticose vein drain?
What does it drain into?
vorticose vein drains vascular layer of eye
drains into superior/inferior opthalmic veins (eventually into cavernous sinus)
You can detect ____ at the optic disc.
Why?
intercranial pressure
because the sclera is continuous with the dura
