Anatomy-The Orbit Flashcards
In the orbit, the medial walls are (blank) to each other and the lateral walls are (blank) to each other
parallel
orthogonal
What is the outpocketing of the forebrain that induces a thickening of the surface ectoderm which will form the lens placode or vesicle?
diencephalic part
What do we consider CN 1 and CN2?
not true cranial nerves
Where do columns stop?
in the midbrain, therefore there are no columns in the forebrain
What is the cornea formed by?
the surface ectoderm
What does the visual retina do?
absorbs light and reduces the amount of bounding around of light
What does the diencephalon form first before forming all the layers of the retina as well as the retinal pigment epithelium and parts of the iris and ciliary body?
the optic cup
What does the optic cup form?
all the layers of the retina as well as the RPE and parts of the iris and ciliary body
What is the muscle of the ciliary body formed by?
mesenchyme that invades the optic cup
What all does the mesenchyme of the eye form?
ciliary muscles, sclera and choroid
The (blank) is the white of the eye, is the opaque, fibrous, protective, outer layer of the eye containing collagen and elastic fiber
sclera
The (blank) is the vascular layer of the eye, containing connective tissue, and lying between the retina and the sclera.
choroid
When the dura reaches the back of the orbit it separates into 2 layers; what are they?
meningeal and periosteal
Which layer of the dura goes to the undersurface of the bone of the top of the orbit?
periosteal
What happens to the meningeal layer of the dura when it reaches the orbit?
it follows the optic nerve and then is continuous with the sclera
Where does the cornea come from?
surface ectoderm and underlying infiltrating mesenchyme
Lens arises from the (blank)
lens placode
What all does the optic cup give rise to?
most of the eye, retina, iris
(blank) invading the area of the optic cup forms smooth muscle, sclera and choroid.
mesenchyme
Cornea comes from (blank)
surface ectoderm
Most severe eye defects are associated with malformation of the (blank)
brain or cranial cavity
cyclopia,anopthalmia
(blank) is a relatively common defect associated with incomplete closure of the choroid fissure, a groove that develops for the invaginating hyaloid artery which later regresses and only remains in the optic nerve as the central artery.
Colomboma
What is the hyaloid artery and what happens to it?
it runs from within the optic nerve to the lens to provide nutrition to the lens in the fetus, but regresses before birth to form the central artery of the optic nerve.
What does the hyaloid artery run through?
The choroid fissure. This is what will remain in colomboma because it fails to close resulting in an abnormality.
Each orbit has what kind of shape?
pyramidal shape
Where is the orbital margin?
Where is the apex of the orbit?
at the base
the optic canal
THe medial walls of the orbit are parallel while the lateral walls of the orbit are at right angles to each other, what does this mean?
this means that the your orbits are facing at angles while your globe is facing straight ahead which means that your optic nerve will be entering medially in your orbit and the fovea will be more lateral
Most of the muscles to the eyeball, will arise from where and attach where and what does this mean?
the back of the orbit, and attach medially. They will be adductors!
What are the bones of the orbit?
frontal zygomatic maxillary lacrimal ethmoid sphenoid palatine
What are the foramen of the sphenoid bone?
optic canal, superior orbital fissure, inferior orbital fissure, foramen ovale, foramen spinosum
Where does the infraorbital nerve lie? How can you easily damage this nerve?
just above the maxillary sinus where it leaves through the infraorbital foramen
blowout fracture
where in your orbit is the lacrimal sac?
Where is the lacrimal gland?
medial
lateral
What are the three layers to the eyeball?
Outer
middle
inner
What makes up the outer layer of the eyeball?
the sclera (opaque) and cornea (translucent)
What makes up the middle layer of the eyeball?
Choroid
ciliary body
Iris
(pigmented layer)
What makes up the inner layer of the eyeball?
retina
has visual and non-visual parts
What kind of epithelium makes up the visual layer of the retina?
Retinal pigment epithelium (RPE)
and non-visual parts
The visual layer of the retina will have what special things?
rods and cones
What are cones for and where do you mostly find them?
high visual acuity; midline of the back of your eye
What are rods for?
night vision and large visual fields
The anterior and posterior chamber of the eye are separated by the (blank)
iris
What suspends the lens in place?
the zonular fibers
What is the vitreous humor/body made up of?
99% water (has hyaloid canal within it)
What is the optic disc?
entry of optic nerve with central retinal vessels
Where do you get a blind spot in your eye?
at the optic disc
Where do you find the largest concentration of cone cells?
the fovea
What is the macula with fovea centralis for?
acute vision
Where do you find the anterior chamber?
in front of the iris
Where do you find the posterior chamber?
behind the iris
What is the vitrous chamber?
large cavity in the eye behind the lens and in front of the retina
Is there a subarachnoid space in the eye and if so, where does it go?
yes, it goes all the way up to the optic disc
What will happen if you have CNS pressure building up behind the eye?
you will get a ring around the optic disc
Where do you find ganglion cells in the eye?
visual layer
How many layers of cells are associated with the retina and what are of significant importance for sending messages to the optic nerve?
about 10
ganglion cells
What happens to the axons of the ganglion cells of the eye?
they will pass over the visual layer and accumulate at the optic disc and enter the optic nerve
Why is the retina less able to pick up light except in the area of the fovea centralis (macula)?
because optic ganglion cells block the ability of the retina to take in light except at the fovea where they are not present
Light rays will focus on the macula, depending on where light is coming from, you will have to change the refractive powers of your eye to get it there. How do you do this?
Shape of cornea (isnt really alterable)
roudness of lens (alterable)
air/water interface (most powerful refractive changer)
What is the natural shape of your lens if you pop it out?
rounded
What is the natural shape of your lens in your eyesocket?
flat because zonal fibers are tightened and holding the lens taught by attached to the ciliary muscle.
What is a flat lens useful for?
far vision
What is a round lens useful for?
up close vision
What is up with nearsightedness?
your pole length is too long for the refractive index
Where does aqueous humor come from and how does it flow?
it comes from the ciliary process to the scleral venous sinus (schlemms canal)
What does the iris do?
pigmented layer, sphincter of pupil, dilator of pupil
What is glaucoma?
increased intraocular pressure (greater than 20-22 mm)
There is a substance in the anterior and posterior chambers called aqueous humor (as opposed to the vitrious humor in the vitrous chamber) this is created by the (blank), then it flows into the ciliary chamber into the posterior chamber over the lens and into the anterior chamber where it is absorbed by the sclerol venous sinus (schlemms canal). Failure to absorb or over production will elevate the pressure of aqueous humor in these chambers. AND cause??????
ciliary process
glaucoma
What are the 2 layers of the iris?
the pigmented layer and the muscle layer
What are the 2 muscles of the iris, how are the fibers arranged, and what are they innervated by?
the sphincter papillae muscles which is circularly arranged (parasympathetics)
the dilator which is radially arranged (sympathetics)
In the eye, which happen faster, parasympathetics or sympathetics?
parasympathetics
cuz you dont want to dilate your eyes quickly or you could blind yourself
The (blank) muscle is a ring of smooth muscle in the eye’s middle layer (vascular layer) that controls accommodation for viewing objects at varying distances and regulates the flow of aqueous humour into Schlemm’s canal.
ciliary
What is ciliary muscle innervated by and how are its fibers oriented?
parasympathetics
circularly (most medial)
radially (most lateral)
How does the ciliary muscle change the shape of the lens?
by reducing the tension of the zonal fibers that support the lens. The circular fibers will contract like a sphincter and reduce the tension on the zonal fibers and the radial fibers will reduce the cross sectional diameter by pulling the whole process towards the sclerocorneal junction which will move the lens forward and thus round up the lens
What meningeal layers cover the optic nerve?
pia mater, arachnoid, and meningeal dura
The deep fascia from the muscles of the superior eyelid form the (blank) which comes off onto the sclero of the eyeball.
bulbar sheath
What muscle goes to the tarsal plates in the superior eyelid?
the levator palpebrae muscle
What is the little tiny layer of muscles that comes from levator palpebrae and attaches to the tarsal plate (helps raise eyelid)? What is this muscle made out of?
Superior tarsal muscle (mueller muscle)
smooth muscle
What basically makes up the eye socket?
the bulbar sheath
What besides the optic nerve comes out of the optic disc?
central artery of retina
The inferior rectus and the inferior oblique make up what ligament?
the suspensory ligament
What is the optic nerve surrounded by? What does increased intracranial pressure show up as around the disc? What do you call this?
CSF, arachnoid, dura
swelling around disc
papilledema (venous congestion, raised disc)
Can you see papilledema unilaterally?
yes, it usually occurs bilaterally but can occur unilaterally in cases of tumor.
Which vessels to you visualize with opthalmoscope?
ciliary vessels
central artery
What artery supplies the iris, ciliary muscle, sclera, rods/cons of retina?
ciliary vessels
What artery supplies the retina?
central artery
What does blockage of the central artery result in?
immediate irreversible blindness
Where does the posterior cilliary artery come off of?
branches off the opthalmic artery
What happens if you get blockage of the posterior ciliary artery?
you will just have some blockage of your rods and cons but you have so many tiny arteries that its not that big of a deal
What CN or nerves participate in the light reflex?
In on CN2 and out on CN3 (or sympathetics)
What CNs participate in the visual blink reflex?
in on 2 out on 7 (orbicularis oculi)
What kind of response do you get when you give stimuli to one eye?
a direct and consensual response between both eyes (i.e blink both eyes if scared, constrict both pupils if you put light into one eye)
The afferent limb coming into your eye, general branches to both (blank) outlets
efferent
If you shine a light in someone’s eye and neither pupil constricts, what kind of problem do you have?
an afferent limb problem
If you shine a light in someone’s eye and one pupil constricts and the other one doesnt then you have what kind of problem?
an efferent limb problem
What 2 things do you do when you accommodate and what fibers carry this out?
you constrict the pupil an change the lens via CN 3 (make more round) both carried out by parasympathetics
What fields of vision does the optic nerve have?
a temporal and nasal field
What happens to the optic nerve when it goes to the chiasms?
there is a crossing of the nasal and temporal fibers
What will the right part of both eyes show you?
the left part of the world
What will the left part of both eyes show you?
the right part of the world
What happens if you cut one optic tract?
you will only see one part of the world (i.e only see the left part or only see the right part)
What happens if you cut out one eyeball?
you will still see the whole world (so better to cut out an entire eye then to cut out an entire tract)
What is located just below the optic chiasm and can sometimes enlarge and press on the optic chiasm?
pituitary gland
What happens if you lose your optic chiasm?
you lose temporal fringe (i.e peripheral vision) because your nasal fibers give you peripheral vision.
the tendons of the muscles that move the eyeball insert into the (blank) of the eyeball.
sclera
what are the 2 disorders associatd with inability to elevate eyelid i.e. cause ptosis?
problem with superior division of oculomotor nerve (levator palpebrae superioris) or problem with sympathetics/autonomics (superior tarsal muscle)
What is the conjunctiva?
the mucous membrane on the inside of the eyelid that is held up by the superior and inferior conjuctival recesses (CT)
Where does the conjunctiva reflect?
onto the globe of the eyeball back onto the sclerocorneal junction
What is ptosis and what causes it?
inability to elevate eyelid
if levator palpebrae superioris or superior tarsal muscle is denervated
How do we get sympathetics to the head (and to the superior tarsal muscles)?
go to sympathetic chain, synapse in superior cervical ganglion and travel on arteries to the head.
What innervates the superior tarsal muscle? What happens if you lose this? what innervates the levator palpebrae superioris?
sympathetics
Horner’s syndrome
superior division of oculomotor nerve
How come in ptosis your eye isn’t completely closed?
because you the orbicularis oculis muscle is need to completely close the eye.
Which is worse, messed up autonomics to the eye or messed up oculomotor nerve to the eye?
occulomotor nerve is worse
What supports the eyeball and is formed by the fascia of the 2 inferior muscles?
suspensory ligament
What do “check ligaments” do?
prevent the eye from moving too far from side to side
What are the four extraocular muscles that originate from a tendinous ring at the apex of the orbit?
superior rectus, inferior rectus, lateral rectus, medial rectus
What arteries and nerves go through the annulus tendineus?
optic nerve, opthalmic artery, oculomotor nerve, nasociliary nerve, abducen nerve,
How does the superior oblique muscle travel?
From behind the eye, and its tendon goes through the trochlea to make a pulley system to allow for abduction
How does the superior oblique move the eyeball?
depresses
medial rotates
abducts
There is a muscle that comes from the bony orbit and parallels the portion of the superior oblique onto the globe except on the inferior side, what is this mystery muscle?
the inferior oblique
How does the inferior oblique move the eyeball?
elevates
laterally rotates
abducts
What muscle is directly underneath the levator palpebrae superioris?
the superior rectus
What nerves innervate the extraocular eye muscles?
LR6(SO4)3
Lateral rectus CN6
Superior oblique CN4
Superior rectus, inferior rectus, inferior oblique, levator palpebrae superiororis
When you are on the AP axis, what kind of movements will the globe undergo?
medial and lateral rotation (internal and external rotation)
When you are on the transverse axis, what kind of movements will the globe undergo?
elevate or depress
What three extraocular muscles are abductors?
lateral rectus, inferior oblique and superior oblique
What three extraocular muscles are adductors?
medial rectus
superior rectus
inferior rectus
What 2 extraocular muscles are elevators?
inferior oblique
superior rectus
What 2 extraocular muscles are depressors?
superior oblique
inferior rectus
What 2 extraocular muscles are med rotators?
superior rectus and superior oblique
What 2 extraocular muscles are lateral rotators?
inferior rectus and inferior oblique
Both the superior rectus and inferior oblique can elevate the eye, so how can you test the function of only the superior rectus?
How can you test the function of only the inferior oblique?
laterally rotate the eye
Medially rotate the eye
What nerves innervate the orbit?
CN 2, 3, 4,51, 6
CN 3, 4, V1 and 6 enter the orbit through what?
the superior orbital fissure
What must 2-6 pass through even though they left the brain stem (and dura) in the posterior fossa?
middle cranial fossa
What travels through the optic foramen?
opthalmic artery and optic nerve (CN 2)
What CN innervates the superior oblique muscle?
CN IV
What are the 2 major branches of V1?
frontal and lacrimal
What nerve does the supratrochlear and supraorbital nerve come off of?
frontal nerve
What kind of fibers does the lacrimal nerve provide?
sensory fibers and postganglionic parasympathetics (from 7)
So since all glands (except parotid) is innervated by CN 7 how is the lacrimal gland innervated by CN 7 when the lacrimal gland is a branch of V1?
because parasympathetics from CN 7 can jump onto the lacrimal
The sensory fibers to the globe is for what structure?
the cornea
What nerves go to the constrictor papillae muscle and the radial and circular muscle of the ciliary muscles?
What fibers innervate these muscles?
the short ciliary nerve from V1
parasympathetics and general somatic sensory
What fibers need go to the dilatory muscles of the of the iris? How do they get there?
sympathetics, get on V1 and goes through supraorbital fissure and then jumps onto long ciliary or short ciliary nerve
What are the 7 branches of V1 (opthalmic division)?
post. ethmoidal
ant. ethmoidal
nasociliary
long ciliary
short ciliary
frontal (splits to supratrochlear and supraorbital)
lacrimal
The frontal nerve is a branch off of (blank) and splits into what 2 nerves?
V1 (opthalamic)
supratrochlear
supraorbital
How do you get parasympathetics to the iris?
they come from CN 3 which jump onto short ciliary nerve
When the ciliary muscle is contracted, then the lens is (blank)
rounded (fat)
When the ciliary muscle is relaxed, then the lens is (blank)
flat
What do the radial fibers of the ciliary muscle do?
pulls the entire ciliary body closer to the scleralcorneal junction and decreases the diameter between these two causing less tension on zonule fibers and rounded lens
What do the circular fibers of the ciliary muscle do?
act like a sphincter to reduce the tension on the zonule fibers
When V1 enters the mid pons, where does it go?
it terminates in either the chief sensory nucleus or sends fibers down to the spinal nucleus of V (if pain or temp)
What are you looking at if the picture looks like a lily pad with a cat face?
(tiger lily)
What is located on the periphery of this?
caudal medulla
spinal trigeminal tract and nucleus
Do you have pre or postganglionic parasympathetics on oculomotor (CN3)? Do you have pre or postganglionic sympathetics on oculomotor (CN3)?
preganglionic
postganglionic
Do parasympathetics travel on the short ciliary nerve or long ciliary nerve?
short ciliary nerve
Do sympathetics travel on the short ciliary or long ciliary?
BOTH!!!
Parasympathetics to (blank) constrict the pupil in response to light.
pupillae
Parasympathetics to (blank) thicken lens for accommodation to near vision
ciliary body
So what cranial nerve is essential for accomodation?
CN 3
Where do parasympathetics synapse on their way to the ciliary body?
ciliary ganglion
Does these short ciliary nerve carry pre or post ganglionics?
post ganglionics
HOw do the sympathetics get to the head?
they have their cell bodies in the lateral horn in T1-T3, travel up the sympathetic chain, synapse in the superior cervical ganglion and jump onto the internal carotid to go to the oculomotor nerve (CN 3)
What muscles make up the annulus tendineus?
all the rectus muscles
Post-ganglionic sympathetics course within the oculomotor nerve to innervate the (blank) that helps elevate upper lid.
superior tarsal muscle
What are the three roots to the ciliary ganglion and what do each of them come from?
sensory-> nasal ciliary (V1)
sympathetic
motor-> (Cn III lower branch)
What muscle does the short ciliary nerve innervate?
the ciliary body and sphincter pupillae muscle
(blank) originate in brainstem and pass through III to levator palpebrae superioris muscle
somatomotor axons
Only (blank) are on the motor root to the ciliary ganglion
parasympathetics
Sympathetics dont only innervate muscle, but also innervates (blank)
blood vessels
How do you block sympathetics to the head?
nerve block at T1-T3 or at the carotid
The following symptoms describe what: constricted pupils ptosis flushed skin (due to lack of vasoconstriction) dry skin
How could you get this?
Horner’s syndrome
Lower brachial plexus injurt
What does the chordi tympani travel on? What does the chordi tympani provide the tongue with? What do the parasympathetics to the tongue travel on? Where do the parasympathetics synpase?
What does the lingual nerve provide to the tongue?
the lingual nerve taste!!!! Chordi tympani and lingual nerve submandibular gland and sublingual gland Sensation to anterior 2/3rds of tongue
Are preganglionic parasympathetics on the lingual nerve or postganglionic parasympathetics?
both
Are preganglionic parasympathetics on the auriculotemporal nerve or postganglionic parasympathetics?
postganglionic parasympathetics
How to parasympathetics get to the parotid gland?
lesser petrosal nerve provides parasympathetics to allow for them to synapse in otic ganglion and give postganglionic parasympathetics to the auriculotemporal (which splits around middle meningeal artery) to give secretomotor to the partod gland
What nerve splits around the middle meningeal artery?
auriculotemporal
Where does the greater petrosal nerve go?
to the lacrimal gland
Where does the nasociliary nerve come from?
V1
What does the oculomotor complex consist of?
oculomotor nucleus and the edinger westphal nucleus
What is it when you see the upside down mickey mouse and what is the whole in the center of it?
level 10-midbrain
aquaduct
The oculomotor nucleus controls all the ye muscles except (blank) and (blank)
lateral rectus and superior oblique
What opens the eyelid?
What closes the eyelid?
CN 3
CN 7
Edinger westphal is a (blank) nucleus and it controls the shape of the lens and constricts the pupil
visceromotor
What does the edinger westphal nucleus do?
controls the shape of the lens and constricts the pupil
Why would the eye be displaced down and out in 3rd nerve damage?
because your LR and your SO will still be intact resulting in down and out
Why would the eyelid be droopy or closed in third nerve damage?
because you lose your superior palpebrae levator and superior tarsal
Why cant a person accommodate for near vision in third nerve damage?
Because your CN3 allows for parasympathetics to get onto the short ciliary nerve to contract the ciliary muscles and allow for a more rounded lens and accomodation. This being knocked out would mean you lost accomodation
How do you often damage CN III?
via space occupying lesions, especially uncal herniation
What is the only cranial nerve to exit the brainstem from the dorsal aspect and cross to the other side?
CN 4
What kind of fibers travel on CN 4?
What does the right nucleus of CN 4 innervate?
GSE
the left superior oblique muscle
What forms the facial colliculus?
Where is the facial colliculus?
It is formed by fibers from the motor nucleus of the facial nerve as they loop over the abducens nucleus.
elevated area located on the dorsal pons in the floor of the 4th ventricle
Where does CN VI leave the pons?
ventrally near the midline
Where is the lacrimal duct located?
laterally
What is the duct that drains the lacrimal gland to the nasal cavity?
nasolacrimal duct
How do you get CN 7 onto the lacrimal gland?
CN 7 gives of greater petrosal nerve which jumps onto V2 and then onto V1 which innervates the lacrimal gland
What are the reflexes that CN 7 innervate?
blinking (corneal and visual) and tearing
Where does the greater petrosal nerve synapse?
in the pterygopalatine ganglion
Where do autonomics from CN 3 synapse and where do their postganglionics go? and what do these fibers do?
ciliary ganglion
short ciliaries
constrict pupil, focus lens
Where do autonomics from T1-3 synapse and where do their postganglionics go? and what do these fibers do?
superior cervical ganglion
short, long ciliaries
dilate pupil
Where do autonomics from CN 7 synapse and where do their postganglionics go? and what do these fibers do?
pterygopalatine
zygomaticotemporal (V2)
to lacrimal (V1)
lacrimal gland secretion
What are the 2 accessory glands of the eye?
the ciliary glands of the eyelashes (sebacous) and the tarsal glands (lipid secreting)
What is signif. about the ciliary glands of the eyelashes?
they are sebaceous and can become infected (sty)
What do the tarsal glands do?
they keep the lid from sticking together and prevent tears from spilling over the lids (liquid/lipid interface)
What are the 5 reflexes of the eye?
corneal blink visual blink pupillary light reflex tearing reflex accommodation reflex
Some of the inferior orbital structures are supplied by the (blank) which comes off the (blank) via the (blank)
infraorbital artery
external carotid
via the maxillary
are there anastomoses between the external and internal carotid?
yes
How does venous blood flow from the orbit?
it drains to the cavernous sinus and the pterygoid plexus of veins
