Sievert: Orbit Flashcards
1
Q
Discuss the orientation of the medial walls of the orbit vs the lateral walls
A
Medial walls of the orbit are parallel to the each other, while the lateral walls are at orthogonal (at a 90 degree angle to one another).
2
Q
What induces the formation of the lens placode or optic vesicle?
A
an outpocketing of the forebrain (diencephalic part)
3
Q
The forebrain outpocketing continues to grow and forms the optic cup which forms all layers of the (blank) as well as the (blank) and parts of the (blank) and (blank)
A
retina; RPE; iris; ciliary body
4
Q
Muscle of the ciliary body is formed by (blank) that invades the optic cup. This (blank) also forms the sclera and choroid
A
mesenchyme
5
Q
(blank) comes from surface ectoderm and the underlying inflitrating mesenchyme. Not the lens placode or optic cup!
A
cornea
6
Q
Lens arises from the (blank)
(blank) gives rise to most of the rest of the eye; retina, iris, etc
(blank) invading the area of the optic cup forms smooth muscle, sclera and choroid
Cornea comes from (blank)
A
lens placode; optic cup; mesenchyme; surface ectoderm
7
Q
Are cranial nerves I and II “true” cranial nerves? Why?
A
No; because there are no columns up in the forebrain - columns stop in the midbrain **these nerves come from an outpocketing of forebrain
8
Q
The eye has 3 embryonic derivatives.
What makes the lens?
What makes the cornea?
What makes the retina, iris, and ciliary body?
A
neural ectoderm
surface ectoderm
outpocketing of brain tissue
9
Q
This is an important part of the retina, which absorbs light and reduces the amount of bouncing around of light at your retina. This allows for visual acuity.
A
RPE
10
Q
What forms the muscle of the ciliary body?
A
surrounding mesenchyme that invades the optic cup
11
Q
Do the lens placode and optic cup give rise to the cornea?
A
No; cornea is from surface ectoderm
12
Q
T/F: Severe eye defects usually accompanied by severe brain deformities, because the optic cup is an outpocketing of the brain.
A
True
13
Q
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.
A
Coloboma
14
Q
What is the shape of each orbit?
Where is the apex?
How are the medial walls oriented?
How are the lateral walls oriented?
A
pyramidal
at the optic canal
parallel to one another
at right angles to one another
15
Q
What is the distance between the two medial walls of the orbits?
A
25mm
16
Q
List the bones of the orbit.
A
frontal zygomatic maxillary lacrimal ethmoid sphenoid palatine
17
Q
What are the openings in the orbit? What bone are they located in? What passes through each opening?
A
- optic canal; sphenoid bone; opthalmic artery and optic nerve
- superior orbital fissure; sphenoid bone; CN 3, 4, 6, and nasociliary, frontal, and lacrimal branches of V1
18
Q
List a few of the sinuses that can be seen in a sagittal view of the orbit.
A
maxillary sinus (inferior to orbit) frontal sinus (above orbit)
19
Q
What happens to the dura when it reaches the optic canal?
A
the two layers of the dura will split, and the meningeal layer will stay with the optic nerve, while the periosteal layer will attach to the bone
20
Q
What are the three layers of the eyeball?
A
- outer layer: sclera (opaque) and cornea (translucent)
- middle layer or pigmented layer: choroid, ciliary body, iris
- inner layer: retina with visual and non-visual parts
21
Q
What are the components of the outer layer of the eyeball?
A
sclera and cornea
22
Q
What are the components of the middle layer of the eyeball?
A
choroid
ciliary body
iris
23
Q
What are the components of the retina (inner layer of the eyeball)?
A
visual layer
non-visual layer
24
Q
(blank) are for high visual acuity. (blank) are more for large receptive fields and night vision
A
cones; rods
25
Eyeball:
What separates the anterior and posterior chambers of the eyeball?
What suspends the lens?
iris
| zonular fibers
26
Which chamber of the eyeball is in front of the iris? Which chamber is behind the iris, but in front of the zonular fibers that attach the lens to the ciliary body?
anterior chamber; posterior chamber
27
What's this?
colorless, transparent gel, 99% water, contains hyaloid canal (a remnant of the regressed hyaloid artery which was a central artery to the lens)
vitreous body
28
What's this?
| entry of optic nerve with central retinal vessels; blind spot
optic disc
29
What's this?
point of highest visual acuity
location where light rays focus when light enters the eyeball
fovea centralis
30
There is a subarachnoid space which goes all the way out to the place where the optic nerve meets the back of the eye. Why is this significant?
When the CSF pressure rises due to a tumor or vascular accident, etc, this can result in an elevated ring around the optic disc.
31
In addition to the rods and cones of the retina, there are about 10 different layers of cells associated with the retina. Which cells have axons which pass over the surface of the retina, accumulate at the optic disc, and enter the optic nerve? What is significant about these cells and the fovea centralis?
ganglion cells
**because they pass along the retina, this makes the retina less able to pick up light in all areas except the fovea centralis. At the fovea centralis, optic ganglion cells do not pass, which makes the retina appear thinner at this location
32
What 3 things determine the refractive power of the eye?
1. shape of the cornea
2. roundness of the lens **can be adjusted
3. air/water interface at the surface of the cornea **greatest refractive ability
33
What is the natural shape of the lens? What must be attached to the lens in order to put it in the eyeball?
round; zonule fibers must be attached to peripheral rim to provide tension and flatten out the lens
34
When the lens is resting in the eye, it is flat. What vision, near or far, is this optimal for? To look at things up close, what must occur?
far vision; lens must round up in order to look at something close up
35
Which pts, near-sighted or far-sighted, are more susceptible to retinal detachment?
near-sighted pts, because the pole between the lens and the fovea is "too long"
36
The flow of aqueous humor is from (blank) to (blank)
ciliary process; Canal of Schlemm
37
Where is the aqueous humor found? Where is it produced?
anterior and posterior chamber;
| produced in the posterior chamber by the ciliary process
38
Fluid from the ciliary process flows freely through the posterior chamber and sneaks between the iris and the lens to the anterior chamber. From there, it is resorbed by the (blank). Failure to absorb aqueous humor will elevate the pressure of aqueous humor in the chambers.
Canal of Schlemm
39
The iris has two layers. What are they?
pigmented layer
| muscle layer **sphincter of pupil and dilator of pupil
40
Increased intraocular pressure (greater than 20-22 mm)
glaucoma
41
The sphincter of the pupil and the dilator of the pupil are both (blank) muscle. The (blank) is circular, while the dilator is radially arranged. What innervates the sphincter of the pupil? What innervates the dilator of the pupil?
smooth; sphincter of pupil; parasympathetics; sympathetics
42
In the eye, (blank) are fast, while (blank) are slow.
parasympathetics; sympathetics **may take 20 minutes to dilate the eye
43
Muscles of the ciliary body have both radial and circular fibers. What are both of these muscle fibers innervated by? What do these muscles do?
parasympathetics; ultimately these fibers round up the lens and create less tension on the zonular fibers
**The circular fibers will contract like a sphincter. When they contract, they relax the zonule fibers. Radial fibers pull the whole ciliary process toward the sclero-corneal junction which moves the lens somewhat forward, and decreases the tension on the zonular fibers
44
What meningeal layers cover the optic nerve as it enters the optic canal?
meningeal layer of the dura, the pia and the arachnoid
45
Muscles of eyeball have an investing fascia, and they form the (blank), which is a continuation of this fascia onto the sclera of the eyeball.
bulbar sheath
46
The tiny muscle that comes off of the levator papebrae superioris, which attaches to the tarsal plate. What is unique about this muscle?
superior tarsis muscles; it is a smooth muscle
47
Where is the point where the optic nerve arises from back of eyeball? What enters the retina at this point? What surrounds the optic nerve?
optic disc; central artery of the retina; CSF, arachnoid, and dura (meningeal layer)
48
What's this?
Can be seen by looking through the pupil at the optic disc with an opthalmoscope.
Usually occurs bilaterally, but can be seen unilaterally in cases of orbital pathology like a tumor.
Venous congestion, raised disc.
papilledema
49
What are the two blood supplies to the eye?
choroid artery
| central artery
50
This artery gets its supply from the ciliary vessels, and supplies the iris, the ciliary muscle, sclera and rods and cones of retina
choroid artery
51
This artery supplies the rest of the retina. Blockage of this artery results in immediate irreversible blindness.
central artery of the retina
52
When looking through an opthalmoscope, what vessels are you looking at?
central arteries
53
In the light reflex, when you shine light on the eye, light travels IN on which nerve and OUT on which nerve? In the dark, light travels in on which nerve and out on what?
in on CN 2 and out on CN 3; in on CN 2 and out on sympathetics
54
When you shine light in one eye, both pupils constrict. There is a direct and a consensual response to light. What is happening?
the afferent limb branches to both efferent outputs
55
What has happened if you shine a light in someone's left eye and see neither of their pupils constrict, but when you shine it in their right eye, both constrict?
there is a break in the afferent limb
56
In the visual blink reflex, info comes IN on which nerve and OUT on which nerve?
in on CN 2 and out on CN 7 **orbicularis occuli causes you to blink
57
In the accommodation reflex, when you are looking at something up close, info comes IN on which nerve and OUT on which nerve?
in on CN 2 and out on CN 3**parasympathetics
58
What two things occur during the accommodation reflex?
1. rounding of the lens
| 2. pupil constriction
59
The optic nerve coming from each eye has two components. What are they?
nasal fiber
| temporal fiber
60
At the optic chiasm, which fibers cross?
nasal fibers
61
Which two fibers contribute to the left optic tract, and allow for vision in the left visual field (left 1/2 of the world)?
right nasal and left temporal fibers
62
If you cut the optic nerve before the optic tract, what will occur?
If you cut the optic tract, what will happen?
What happens if you cut the nasal fibers as they cross at the optic chiasm?
blindness in one eye;
you will lose 1/2 of the world;
you will lose monocular vision (unless you close one eye, in which case you will only see 1/2 of the world)
63
What happens when there is a pituitary tumor pressing down on the optic chiasm?
you will lose the right and left nasal fibers, so you will lose the temporal fringe, or the monocular area (lateral-most area in each visual field)
64
What two muscles attach to the tarsal plate?
superior tarsal muscle
| levator palpebrae superioris
65
What kind of muscle is the superior tarsal muscle?
What is it innervated by?
What does it do?!
smooth muscle;
innervated by sympathetics;
keeps your eyelid up
66
There are 2 disorders that could be present when a patient presents with inability to elevate their eyelid. What could they be?
1. problem with superior division of occulomotor nerve to levator palebrae
2. problem with sympathetics to the superior tarsus muscle
67
What is ptosis of the eyelid most commonly associated with?
Horner's syndrome **damage of sympathetic outflow to head and neck
68
Can occur if either levator palpebrae superioris or the superior tarsal muscle is denervated
ptosis
69
The sheath of these two muscles has a thickening which forms up the suspensory ligament of the eyeball, which helps hold the eyeball in place.
inferior oblique
| inferior rectus
70
This is a mucous membrane lining the inside of the eyelid. It is held up by a slip of investing fascia at the superior and inferior conjunctival recesses, and reflects onto the globe of the eyeball back to the sclero-corneal junction. It creates a sac.
conjunctiva
71
Which is more severe: ptosis from a broken occulomotor nerve or from sympathetics?
• Ptosis from a broken occulomotor nerve is more severe. Results in no muscular ability of eyelid, so eyelid will cover over a portion of the pupil. In order to completely close the eyelid, need the obicularis occuli to elevate the bottom lid a bit. With sympathetic ptosis, just a droopy eyelid.
72
What innervates the superior tarsus muscle?
sympathetics
73
What innervates the levator palpebrae?
occulomotor nerve
74
These ligaments prevent the eye from moving too far from side to side. Which prevents over-adduction? Which prevents over-abduction?
medial and lateral check ligaments
* *medial prevents over adduction
* *lateral prevents over abduction
75
This is a tendinous ring at the apex of the orbit, where 4 of the extraoccular muscles originate.
annulus tendineus
76
What 4 muscles arise from and insert into the annulus tendineus?
superior, inferior, medial, and lateral rectus
77
What two important things pass through the annulus tendineus to enter the eye?
optic nerve
| ophthalmic artery
78
Which muscle attaches to the superior tarsal plate? Where do all other muscles attach?
levator palpebrae; to the sclera of the eye
79
Where do the muscles that arise from the back of the eyeball attach? What about the muscles that arise from the front?
All of the muscles from the back of the eyeball will attach to the front half of the eyeball. All muscles that arise from the front will attach to the back half of the eyeball.
80
What is unique about the superior oblique muscle?
it is one of the two muscles whose functional attachment is from the front of the orbit, it has a portion which passes through a sling or a pulley, and parallels the inferior oblique
81
Muscles that arise from the posterior functional orbit attach to the (blank) half of the eyeball.
Muscles with functional attachment at the front of the orbit attach at the (blank) half of the eyeball.
anterior; posterior
82
What nerve innervates the lateral rectus muscle?
CN 6
83
What nerve innervates the superior oblique muscle?
CN 4
84
What are all other muscles of the eye innervated by?
CN 3 *including levator palpebrae
85
Eye movements occur on 3 axes. What are they? What actions do they allow?
AP axis: allows for medial and lateral rotation
transverse axis: elevates and depresses
vertical axis: abduct or adduct
86
Which extraocular muscles perform adduction?
medial rectus
superior rectus
inferior rectus
87
Which extraocular muscles perform abduction?
lateral rectus
inferior oblique
superior oblique
88
Which extraocular muscles elevate the eye?
superior rectus
| inferior oblique
89
Which extraocular muscles depress the eye?
inferior rectus
| superior oblique
90
Which extraocular muscles are medial rotators?
superior rectus
| superior oblique
91
Which extraocular muscles are lateral rotators?
inferior rectus
| inferior oblique
92
Both the superior rectus and the inferior oblique can elevate the eye. So, how can you determine which is dysfunctional?
If you adduct the eye and then look up, only the inferior oblique can work (superior rectus will be in line with the axis, so it is not capable of elevating, superior rectus can adduct, but not at the same time as it elevates).
If you abduct the eye and then look up, only the superior rectus can work
93
What nerves enter the orbit?
CN 2, 3, 4, V1, and 6;
94
What structures pass through the optic foramen?
optic nerve and ophthalmic artery
95
What structures pass through the superior orbital fissure?
CN 3, 4, V1, and 6
96
What eye muscle does CN 4 innervate?
superior oblique
97
What are the two major branches of the ophthalmic division of CN 5? What is the third main branch of of V1?
frontal *which branches into supratrochlear and supraorbital;
lacrimal;
nasociliary
98
What eye muscles does CN 6 innervate?
lateral rectus
99
The lacrimal nerve carries (blank) from CN 7
postganglionic parasympathetics to the lacrimal gland
100
Where does the nasociliary nerve branch off of V1? The nasociliary gives off end branches that supply the mucosa of the (blank). It also gives of (blank) nerves to the back of the eye.
near the superior orbital fissure;
ethmoid air cells *anterior and posterior ethmoidal nerves;
long and short ciliary *sympathetics also carried on the long and short ciliary
101
What is responsible for the synapse between pre and post-ganglionic parasympathetics near the orbit?
ciliary ganglion
102
Where do branches of CN 3 go?
to all other extraoccular muscles and to the ciliary ganglion
103
What comes off of CN 3, carries preganglionic parasympathetics, synapses in the ciliary ganglion, and takes the short ciliary nerves to reach the globe?
motor root to the ganglion
104
CN V1 is only sensory and comes out of which cell column in the brainstem?
general somatic afferent (GSA)
105
What are the three main branches of V1?
nasociliary
frontal
lacrimal
106
What opening does V1 pass through?
superior orbital fissure
107
Where does the nasociliary nerve go?
to the ethmoid bone to supply the ethmoid air cells
108
What are the two branches of the frontal nerve?
supratrochlear
| supraorbital
109
What does the lacrimal nerve supply?
the lacrimal gland **SENSORY
110
What supplies sensory innervation to the cornea?
sensory fibers that pass through the ciliary ganglion without synapsing
111
Parasympathetics from CN 3 synapse in the ciliary ganglion, jump on the short ciliary nerve of CN 5, travel to the back of the eyeball and supply which muscles?
constrictor pupilli
| radial and circular fibers of the ciliary muscle
112
How do sympathetics get to the eyeball?! What muscle do the sympathetics innervate?
Sympathetics can enter by jumping on short ciliary nerves, or staying with the long ciliaries which also enter the eyeball. Sympathetics will only go to the dilator papillae muscle once in the eyeball.
113
When the ciliary muscles contract, what happens to the lens? What happens when they relax?
It becomes relaxed and rounds up (allows for closer vision);
| the lens flattens
114
Radial fibers pull the entire ciliary body closer to the (blank) (decreased diameter) also resulting in less tension on zonule fibers.
Circular fibers act like a (blank) to reduce the tension on the zonule fibers.
scleral-corneal junction; sphincter
115
Where does V1 enter the brainstem? Where does it terminate?
in the pons; chief sensory or spinal nucleus of 5
116
CN 3 carries parasympathetics to what muscle? What does this muscle do?
sphincter pupillae muscle; constricts pupil in response to light;
ciliary body: thickens lens for accomodation for near vision
117
Do somatomotor axons traveling on CN 3 synapse in the ciliary ganglion?
no, they have no reason to synapse
| only the motor root to the ganglion will synapse at the ciliary ganglion
118
How do sympathetics enter the cranial cavity? Are they preganglionic or post?
on the internal carotid arteries; POSTGANGLIONIC *they synapsed back in the superior cervical ganglion
119
Post-ganglionic sympathetics course within oculomotor nerve to innervate what muscle? They also travel along the long and short ciliary branches of V1 to what muscle?
superior tarsal muscle *elevates eyelid
| dilator pupillae *dilates pupil
120
In addition to the superior tarsal muscle and the dilator pupillae, what else do sympathetics to the globe supply?
blood vessels!
121
What's this?
| Injury to or loss of sympathetics from the superior cervical ganglion
Horner's syndrome
122
4 symptoms of Horner's syndrome and their causes
1. constricted pupil: loss of dilator pupillae
2. ptosis: loss of superior tarsal muscle
3. flushed skin: loss of vasoconstriction
4. dry skin: loss of sweat glands
123
What's this?
| Shine light in patients eyes (optic n.) and pupil should constrict (parasymp via III) via sphincter pupillae muscle.
Light reflex
| **has both a parasympathetic and a sympathetic response, but usually only the parasympathetic response is tested
124
What's this?
As patient looks from a far to near object (optic n.), lens should thicken for focusing on near object by contraction of ciliary muscles (parasymp via III).
Accommodation reflex
125
What does the oculomotor complex consist of?
oculomotor nucleus
| Edinger Westphal nucleus
126
What does the oculomotor nucleus do? Does it open the eyelid?
controls all eye muscles except the lateral rectus and superior oblique
it opens the eyelid, but CN 7 closes it
127
What is the Edinger Westphal nucleus?
a visceromotor nucleus associated with CN 3 that controls the shape of and constricts the pupils
128
Is CN 3 easily damaged? How? What is the most common cause of damage?
yes, following space occupying lesions of the cerebral hemispheres; uncal herniation (herniation of the uncus) is the most common cause of nerve damage here
129
Only CN to exit the brainstem from the dorsal aspect and cross to other side.
CN 4
130
What cranial nerve component does CN4 carry? Where does this nerve pass through? What does it innervate?
somatomotor; superior orbital fissure; superior oblique
131
2 reasons why CN 4 is unique?
CN IV nucleus is (GSE) sits in the midline and is the ONLY CN to exit the DORSAL aspect of the brainstem. Also unique because the right nucleus innervates the left superior oblique muscle **crossing over
132
What passes over the abducens nucleus?
the motor root of CN 7 as it forms the facial colliculus
133
Where does CN 6 leave the brainstem?
ventrally, near the midline, in the pons
134
What innervates the lacrimal gland?
| What are the components of the lacrimal gland?
CN 7;
| gland with ducts, lacrimal sac, nasolacrimal duct which drains to the nasal cavity
135
How does the greater petrosal branch of CN 7 reach the lacrimal gland?
it jumps on V2 and then V1
136
What are the three sources of autonomics to the orbit?
CN 3
T1-3
CN 7
137
Where do fibers from CN 3 synapse on their way to the orbit? How do postganglionics reach the orbit? What effect does CN 3 have on the orbit?
synapses at the ciliary ganglion; travels on short ciliaries; constricts pupil and focuses lens
138
Where do sympathetics from T1-3 synapse on their way to the orbit? How do postganglionics reach the orbit? What actions to sympathetics to the orbit have?
synapse at the superior cervical ganglion; travel on short and long ciliaries to the orbit; dilate the pupil
139
WHY does CN 7 go to the eye? What cranial component does it provide? Where do fibers from CN 7 synapse on their way to the orbit? How do postganglionics reach the orbit? What action do postganglionics have on the eye?
to innervate the lacrimal gland; visceromotor; pterygopalatine; travel on zygomaticotemporal nerve (V2), then hop on the lacrimal (V1); SECRETION of lacrimal gland
140
What are the two accessory glands of the eye?
ciliary glands of eyelashes **can become infected (sty)
| tarsal glands **keep the lids from sticking together and prevent tears from spilling over the lids
141
What artery supplies the eyeball?
ophthalmic artery off of the internal carotid
142
What artery supplies some inferior orbital structures?
infraorbital artery off of the external carotid via the maxillary
143
Where does blood flow from the orbit normally drain?
to the cavernous sinus and the pterygoid plexus of veins
144
T/F: There are anastomotic connections between the internal carotid and external carotid branches in the orbit just like we saw in the face
True
