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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
Q

What are the three primary muscles associated with the eyelids?

A

levator palpebrae superioris

superior tarsal muscle

orbicularis oculi

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26
Q

What two muscles are responsible for opening the eyelids?

A

levator palpebrae superioris (stronger)

superior tarsal muscle

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27
Q

Where does the levator palpebrae superioris insert?

A

inserts onto skin of eyelid

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28
Q

What innervates the levator palpebrae superioris?

A

oculomotor nerve (CN III)

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29
Q

What is the origin and insertion of the superior tarsal muscle?

A

origin = underside of levator palpebrae superioris

insertion = tarsal plate

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30
Q

What innervates the superior tarsal muscle?

A

sympathetic fibers from the superior cervical ganglion

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31
Q

What muscle is responsible for closing the eyelids?

A

orbicularis oculi

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32
Q

What innervates the orbicularis oculi?

A

facial nerve (CN VII)

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33
Q

What are the major functions of eye moisture? (2)

A

keep cornea and conjunctiva moist

remove irritants

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34
Q

Describe the significance of the lacrimal gland in tear production.

A

lacrimal gland secretes lacrimal fuid, the primary aqueous component of the tear film

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35
Q

Describe the nutrient-providing function of lacrimal fluid in tears.

A

provides nutrients and dissolved O2 for avascular cornea

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36
Q

What are tarsal glands?

A

modified sebaceous glands embedded in tarsal plates

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37
Q

What do tarsal glands produce? (2)

A

oily secretion that:

contributes to tear film

lubricates edges of eyelids

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38
Q

Describe the drainage pathway associated with the lacrimal gland of orbit. (7)

A

lacrimal gland → superior/inferior puncta → canaliculi → lacrimal sac → nasolacrimal duct → inferior nasal meatus → nasal cavity

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39
Q

Describe the pathway of innervation to the lacrimal gland. (5)

A

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

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40
Q

What is Tenon’s capsule/bulbar fascia?

A

thin fascial sheath enveloping globe, from optic nerve to corneoscleral junction

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41
Q

What is the function of Tenon’s capsule/bulbar fascia?

A

forms socket (support) for globe

separates globe from orbital fat

checks and coordinates movements of ocular muscles

42
Q

What are the three axes of global movement? List the movements associated with each axis.

A

transverse axis = elevation, depression

vertical axis = medial/adduction, lateral/abduction

longitudinal axis =

43
Q

What are the six extrinsic extraocular muscles?

A

in pairs of antagonists:

superior and inferior rectus

medial and lateral rectus

superior and inferior oblique

44
Q

What is the annulus of Zinn?

A

fibrous ring surrounding optic canal that is part of superior orbital fissure

45
Q

What is the origin of all the extraocular rectus (superior/inferior/medial/lateral) muscles?

A

annulus of Zinn

46
Q

What is the origin of the levator palpebrae superioris?

A

bone near optic canal

47
Q

What is the origin of the superior oblique (an extraocular muscle)?

A

bone near optic canal

48
Q

What is the origin of the inferior oblique?

A

antero-medial aspect of orbital floor

49
Q

Describe the movements/actions associated with the superior and inferior rectus, which are EOMs.

A

elevation (superior rectus)

depression (inferior rectus)

50
Q

Describe the movements/actions associated with the medial and lateral rectus, which are EOMs.

A

adduction (medial rectus)

abduction (lateral rectus)

51
Q

Describe the movements/actions associated with the superior and inferior obliques, which are EOMs.

A

depression (superior oblique - moves pupil down and out)

elevation (inferior oblique - moves pupil up and out)

52
Q

When do the superior and inferior obliques (EOMs) function more efficiently?

A

when the globe has already been adducted by the medial rectus

53
Q

When do the superior and inferior rectus (EOMs) function more efficiently?

A

when the globe has already been abducted by the lateral rectus

54
Q

Sketch a diagram of the six tests of extraoecular eye movements. List the associated muscle for each movement.

A
55
Q

List the sources of innervation for the six extraocular muscles.

A

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
Q

What muscles of the orbit does CN III innervate?

A

superior ramus of CN III:

levator palpebrae superioris

superior rectus

inferior ramus of CN III:

inferior rectus

medial rectus

inferior oblique

57
Q

The levator palpebrae superioris is innervated by

A

the superior ramus of CN III

58
Q

What divisions of the trigeminal nerve are relevant to the orbit? (1 +3, 1 +2)

A

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
Q

How does the frontal nerve further subdivide in the context of the orbit?

A

frontal nerve → supratrochlear + supraorbital nerve

60
Q

Describe the function of the two branches of the frontal nerve in the context of the orbit.

A

supratrocheal nerve (more medial) = sensory supply to upper eyelid and forehead

supraorbital nerve (more lateral) = sensory supply to upper eyelid, forehead, and scalp

61
Q

What is the function of the lacrimal nerve in the context of the orbit? (2)

A

sensory supply to upper eyelid

carries postganglionic parasympathetic fibers to lacrimal gland

62
Q

What is the function of the nasociliary nerve in the context of the orbit? (2)

A

sensory to eyeball (especially cornea) via long ciliary branches

sensory to anterosuperior part of nasal cavity

63
Q

Arrange the subdivisions of the opthalmic division of the trigeminal nerve (CN V1) in terms of position.

A

frontal = largest and most superior

lacrimal = most lateral

nasociliary = most inferior and medial

64
Q

What is the function of the infraorbital nerve in the context of the orbit?

A

sensory supply to:

upper lip

lower eyelid

upper dentition

65
Q

What is the function of the zygomatic nerve in the context of the orbit?

A

sensory to skin of cheekbone

carries postganglionic parasympathetic fibers to lacrimal gland

66
Q

What is the ciliary ganglion?

A

parasympathetic ganglion for smooth muscle of eyelid

67
Q

What are the three concentric layers of the globe?

A

outer fibrous layer = sclera + cornea

middle vascular layer = choroid + ciliary body + iris

inner sensory layer = retina

68
Q

What are the three chambers of the globe?

A

anterior chamber (anterior to iris)

posterior chamber (posterior to iris)

vitreous chamber (behind lens)

69
Q

What structure demarcates the boundaries of the anterior and posterior chambers of the globe?

A

iris

70
Q

What is the major refractory element of the eye?

A

lens

71
Q

What is the function of aqueous humor? (3)

A

provides nutrients for avascular cornea + lens

removes metabolic waste products

generates intraocular pressure to maintain shape of globe

72
Q

What is the function of the vitreous chamber?

A

holds retina in place

supports lens

transmits light

73
Q

What is the limbus (of the eye)?

A

transition zone between sclera and cornea

74
Q

What is the sclera? (2)

A

whites of the eye

provides attachment for extraocular and intrinsic muscles of the eye

75
Q

What is the choroid?

A

pigmented and highly vascular structure that lines sclera

76
Q

What is the function of the ciliary body?

A

anchors lens and controls its shape

thus controls focus of the lens

77
Q

The ciliary processes attach to

A

the suspensory ligament of the lens (after crossing through the posterior chamber)

78
Q

The ciliary processes secrete

A

aqueous humor

79
Q

What structure holds the lens in the pathway of light?

A

suspensory ligaments

80
Q

What is the function of ciliary muscle?

A

moves ciliary body forward and inward → decreases tension on zonular fibers → lens more spherical → better focus on retina

81
Q

Is the ciliary muscle innervated via a sympathetic or parasympathetic pathway?

A

parasympathetic

82
Q

What is the function of the iris?

A

regulates the size of the pupil and therefore controls amount of light reaching the retina

83
Q

What are the two muscles associated with the iris?

A

sphincter (constrictor) pupillae muscle

dilator pupillae muscle

84
Q

Differentiate between the sphincter pupillae and dilator pupillae muscles in terms of structure and innervation.

A

sphincter pupillae muscle = circular fibers + parasympathetic innervation

dilator pupillae = radial fibers + sympathetic innervation

85
Q

The retina belongs to what nervous system?

A

the retina is part of the CNS

86
Q

What is the optic disc?

A

“blind spot”

site where the optic nerve joins the retina

87
Q

What vessel supplies blood to most of the retina?

A

central artery of retina

88
Q

What is the ora serrata?

A

anterior termination of neural part of retina

89
Q

In the context of the eye, what is accommodation?

A

process by which eye changes focus from distant to near objects by changing shape of lens

90
Q

What muscle actions are associated with accommodation of the lens?

A

contraction of medial rectus muscles

constriction of pupil by sphincter pupillae muscle

91
Q

What is the “near triad?”

A

accommodation

contraction of rectus muscles

miosis

92
Q

What is miosis?

A

constriction of pupils

93
Q

Describe the innervation pathway of the “near triad” of the eye.

A

under parasympathetic control:

preganglionic = oculomotor nerve

ganglion = ciliary ganglion

postganglionic = short ciliary nerves that travel to ciliary and sphincter pupillae muscles

94
Q

How does a sympathetic response affect the eye? (2)

A

upper eyelids retract by superior tarsal muscles

pupils open widely by dilator pupillae muscle

95
Q

Horner’s syndrome is caused by

A

loss of sympathetic innervation to the face

96
Q

What are the three classic symptoms of Horner’s syndrome?

A

right eyelid ptosis = eyelid drooping

anhidrosis = absence of sweating

right eyelid miosis = constriction of pupil

97
Q

What can cause the loss of sympathetic innervation to the face that results in Horner’s syndrome? (3)

A

secondary brain injury

damage to cervical sympathetic trunk

Pancost tumor

98
Q

If you have partial ptosis, which muscle is nonfunctional? Which muscle is dominating?

A

nonfunctional = levator palepbrae superioris

dominating = superior tarsal

99
Q

If a pupil is dilated but won’t constrict, which muscle is nonfunctional? Which is dominating?

A

nonfunctional = sphincter pupillae out

dominating = dilator pupillae

100
Q

If the pupil is held down and out, which muscles are not working? Which are working?

A

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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