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Human Structure - Block 2 > HS2-9 Eye > Flashcards

HS2-9 Eye Flashcards

1
Q

Describe the volume composition of the orbit. (3)

A

eyeball (globe) = 20%

fat = 50-60%

remainder = muscles, nerves, vessels

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2
Q

Where is the diameter of the orbit greatest?

A

behind rim

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3
Q

What separates the two orbits? (2)

A

ethmoidal sinuses

upper part of nasal cavity

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4
Q

The superior orbital fissure leads to

A

the middle cranial fossa

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5
Q

What structures pass through the superior orbital fissure? (5)

A

CN III

CN IV

CN V1

CN VI

ophthalmic vein

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6
Q

The optic canal leads to

A

the middle cranial fossa

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7
Q

What structures pass through the optic canal? (2)

A

optic nerve

ophthalmic artery (a branch of internal carotid)

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8
Q

The inferior orbital fissure leads to (2)

A

infratemporal fossa

pterygopalatine fossa

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9
Q

What structures pass through the inferior orbital fissure? (3)

A

zygomatic nerve (branch of V2)

infraorbital nerve (branch of V2)

maxillary vessels

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10
Q

Describe the pathway of structures that leads to the infraorbital foramen.

A

infraorbital groove → infraorbital canal → infraorbital foramen

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11
Q

What structures pass through the infraorbital foramen?

A

infraorbital neurovascular bundle

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12
Q

The nasolacrimal canal leads to

A

the nasal cavity

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13
Q

What structures pass through the nasolacrimal canal?

A

nasolacrimal duct

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14
Q

The ethmoidal foramina lead to

A

the nasal cavity

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15
Q

What structures pass through the ethmoidal foramina? (2)

A

branches of V1

ophthalmic vessels

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16
Q

Describe the outer layer of the eyelid.

A

thin skin

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17
Q

Describe the inner layer of the eyelid.

A

lined with transparent inner mucous membrane = conjunctiva

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18
Q

The conjunctiva of the eyelid is continuous with

A

the epithelium of the cornea

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19
Q

The inner and outer layers of the eyelids enclose what space?

A

conjunctival sac

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20
Q

What is the functional advantage of the conjunctiva?

A

conjunctiva allows eyelid to move more easily over globe

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21
Q

What two structures comprise the skeleton of the eyelid?

A

orbital septum

tarsal plates

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22
Q

What is the orbital septum?

A

fibrous membrane continuous with orbital periosteum

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23
Q

What are tarsal plates?

A

dense bands of fibrocartilage that give eyelids their rounded shape

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24
Q

What structure is responsible for giving eyelids their rounded shape?

A

tarsal plates

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25
What are the three primary muscles associated with the eyelids?
levator palpebrae superioris superior tarsal muscle orbicularis oculi
26
What two muscles are responsible for opening the eyelids?
levator palpebrae superioris (stronger) superior tarsal muscle
27
Where does the levator palpebrae superioris insert?
inserts onto skin of eyelid
28
What innervates the levator palpebrae superioris?
oculomotor nerve (CN III)
29
What is the origin and insertion of the superior tarsal muscle?
origin = underside of levator palpebrae superioris insertion = tarsal plate
30
What innervates the superior tarsal muscle?
sympathetic fibers from the superior cervical ganglion
31
What muscle is responsible for closing the eyelids?
orbicularis oculi
32
What innervates the orbicularis oculi?
facial nerve (CN VII)
33
What are the major functions of eye moisture? (2)
keep cornea and conjunctiva moist remove irritants
34
Describe the significance of the lacrimal gland in tear production.
lacrimal gland secretes lacrimal fuid, the primary aqueous component of the tear film
35
Describe the nutrient-providing function of lacrimal fluid in tears.
provides nutrients and dissolved O2 for avascular cornea
36
What are tarsal glands?
modified sebaceous glands embedded in tarsal plates
37
What do tarsal glands produce? (2)
_oily secretion that:_ contributes to tear film lubricates edges of eyelids
38
Describe the drainage pathway associated with the lacrimal gland of orbit. (7)
lacrimal gland → superior/inferior puncta → canaliculi → lacrimal sac → nasolacrimal duct → inferior nasal meatus → nasal cavity
39
Describe the pathway of innervation to the lacrimal gland. (5)
preganglionic secretomotor fibers conveyed by _greater petrosal nerve_ (branch of CN VII) then conveyed by nerve of pterygoid canal synapse and pterygopalatine ganglion postganglionic fibers travel with zygomatic nerve (branch of CN V2) then travel with lacrimal nerve (branch of CN V1) to lacrimal gland
40
What is Tenon's capsule/bulbar fascia?
thin fascial sheath enveloping globe, from optic nerve to corneoscleral junction
41
What is the function of Tenon's capsule/bulbar fascia?
forms socket (support) for globe separates globe from orbital fat checks and coordinates movements of ocular muscles
42
What are the three axes of global movement? List the movements associated with each axis.
transverse axis = elevation, depression vertical axis = medial/adduction, lateral/abduction longitudinal axis =
43
What are the six extrinsic extraocular muscles?
*in pairs of antagonists:* superior and inferior rectus medial and lateral rectus superior and inferior oblique
44
What is the annulus of Zinn?
fibrous ring surrounding optic canal that is part of superior orbital fissure
45
What is the origin of all the extraocular rectus (superior/inferior/medial/lateral) muscles?
annulus of Zinn
46
What is the origin of the levator palpebrae superioris?
bone near optic canal
47
What is the origin of the superior oblique (an extraocular muscle)?
bone near optic canal
48
What is the origin of the inferior oblique?
antero-medial aspect of orbital floor
49
Describe the movements/actions associated with the superior and inferior rectus, which are EOMs.
elevation (superior rectus) depression (inferior rectus)
50
Describe the movements/actions associated with the medial and lateral rectus, which are EOMs.
adduction (medial rectus) abduction (lateral rectus)
51
Describe the movements/actions associated with the superior and inferior obliques, which are EOMs.
depression (superior oblique - moves pupil down and out) elevation (inferior oblique - moves pupil up and out)
52
When do the superior and inferior obliques (EOMs) function more efficiently?
when the globe has already been adducted by the medial rectus
53
When do the superior and inferior rectus (EOMs) function more efficiently?
when the globe has already been abducted by the lateral rectus
54
Sketch a diagram of the six tests of extraoecular eye movements. List the associated muscle for each movement.
55
List the sources of innervation for the six extraocular muscles.
superior rectus = superior ramus of CN III inferior rectus = inferior ramus of CN III lateral rectus = CN VI (think LR6) medial rectus = inferior ramus of CN III superior oblique = CN IV (think SO4) inferior oblique = inferior ramus of CN III
56
What muscles of the orbit does CN III innervate?
_superior ramus of CN III:_ levator palpebrae superioris superior rectus _inferior ramus of CN III:_ inferior rectus medial rectus inferior oblique
57
The levator palpebrae superioris is innervated by
the superior ramus of CN III
58
What divisions of the trigeminal nerve are relevant to the orbit? (1 +3, 1 +2)
_opthalmic division of trigeminal nerve (CN V1)_, which further branches into: frontal nerve lacrimal nerve nasociliary nerve _maxillary division of trigeminal nerve (CN V2)_, which further branches into: infraorbital nerve zygomatic nerve
59
How does the frontal nerve further subdivide in the context of the orbit?
frontal nerve → supratrochlear + supraorbital nerve
60
Describe the function of the two branches of the frontal nerve in the context of the orbit.
supratrocheal nerve (more medial) = sensory supply to upper eyelid and forehead supraorbital nerve (more lateral) = sensory supply to upper eyelid, forehead, and scalp
61
What is the function of the lacrimal nerve in the context of the orbit? (2)
sensory supply to upper eyelid carries postganglionic parasympathetic fibers to lacrimal gland
62
What is the function of the nasociliary nerve in the context of the orbit? (2)
sensory to eyeball (especially cornea) via long ciliary branches sensory to anterosuperior part of nasal cavity
63
Arrange the subdivisions of the opthalmic division of the trigeminal nerve (CN V1) in terms of position.
frontal = largest and most superior lacrimal = most lateral nasociliary = most inferior and medial
64
What is the function of the infraorbital nerve in the context of the orbit?
sensory supply to: upper lip lower eyelid upper dentition
65
What is the function of the zygomatic nerve in the context of the orbit?
sensory to skin of cheekbone carries postganglionic parasympathetic fibers to lacrimal gland
66
What is the ciliary ganglion?
parasympathetic ganglion for smooth muscle of eyelid
67
What are the three concentric layers of the globe?
outer fibrous layer = sclera + cornea middle vascular layer = choroid + ciliary body + iris inner sensory layer = retina
68
What are the three chambers of the globe?
anterior chamber (anterior to iris) posterior chamber (posterior to iris) vitreous chamber (behind lens)
69
What structure demarcates the boundaries of the anterior and posterior chambers of the globe?
iris
70
What is the major refractory element of the eye?
lens
71
What is the function of aqueous humor? (3)
provides nutrients for avascular cornea + lens removes metabolic waste products generates intraocular pressure to maintain shape of globe
72
What is the function of the vitreous chamber?
holds retina in place supports lens transmits light
73
What is the limbus (of the eye)?
transition zone between sclera and cornea
74
What is the sclera? (2)
whites of the eye provides attachment for extraocular and intrinsic muscles of the eye
75
What is the choroid?
pigmented and highly vascular structure that lines sclera
76
What is the function of the ciliary body?
anchors lens and controls its shape thus controls focus of the lens
77
The ciliary processes attach to
the suspensory ligament of the lens (after crossing through the posterior chamber)
78
The ciliary processes secrete
aqueous humor
79
What structure holds the lens in the pathway of light?
suspensory ligaments
80
What is the function of ciliary muscle?
moves ciliary body forward and inward → decreases tension on zonular fibers → lens more spherical → better focus on retina
81
Is the ciliary muscle innervated via a sympathetic or parasympathetic pathway?
parasympathetic
82
What is the function of the iris?
regulates the size of the pupil and therefore controls amount of light reaching the retina
83
What are the two muscles associated with the iris?
sphincter (constrictor) pupillae muscle dilator pupillae muscle
84
Differentiate between the sphincter pupillae and dilator pupillae muscles in terms of structure and innervation.
sphincter pupillae muscle = circular fibers + parasympathetic innervation dilator pupillae = radial fibers + sympathetic innervation
85
The retina belongs to what nervous system?
the retina is part of the CNS
86
What is the optic disc?
"blind spot" site where the optic nerve joins the retina
87
What vessel supplies blood to most of the retina?
central artery of retina
88
What is the ora serrata?
anterior termination of neural part of retina
89
In the context of the eye, what is accommodation?
process by which eye changes focus from distant to near objects by changing shape of lens
90
What muscle actions are associated with accommodation of the lens?
contraction of medial rectus muscles constriction of pupil by sphincter pupillae muscle
91
What is the "near triad?"
accommodation contraction of rectus muscles miosis
92
What is miosis?
constriction of pupils
93
Describe the innervation pathway of the "near triad" of the eye.
_under parasympathetic control:_ preganglionic = oculomotor nerve ganglion = ciliary ganglion postganglionic = short ciliary nerves that travel to ciliary and sphincter pupillae muscles
94
How does a sympathetic response affect the eye? (2)
upper eyelids retract by superior tarsal muscles pupils open widely by dilator pupillae muscle
95
Horner's syndrome is caused by
loss of sympathetic innervation to the face
96
What are the three classic symptoms of Horner's syndrome?
right eyelid ptosis = eyelid drooping anhidrosis = absence of sweating right eyelid miosis = constriction of pupil
97
What can cause the loss of sympathetic innervation to the face that results in Horner's syndrome? (3)
secondary brain injury damage to cervical sympathetic trunk Pancost tumor
98
If you have partial ptosis, which muscle is nonfunctional? Which muscle is dominating?
nonfunctional = levator palepbrae superioris dominating = superior tarsal
99
If a pupil is dilated but won't constrict, which muscle is nonfunctional? Which is dominating?
nonfunctional = sphincter pupillae out dominating = dilator pupillae
100
If the pupil is held down and out, which muscles are not working? Which are working?
not working = superior rectus, inferior rectus, medial rectus, inferior oblique working = lateral rectus, superior oblique

Human Structure - Block 2 (22 decks)

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