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Funk Anatomy - NS Exam 3 > Eye and Orbit > Flashcards

Eye and Orbit Flashcards

1
Q

Describe the depth, width, and shape of the orbits and their positions relative to each other.

A

They are twice as deep as they are wide. Shaped like quadrangular pyramids with the apex at the posterior. The medial walls of the orbits are parallel to each other while the lateral walls are perpendicular.

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2
Q

What are the seven bones which form the orbit?

A

sphenoid, ethmoid, frontal, maxillary, zygomatic, lacrimal, and palatine

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3
Q

Apex of the orbit is formed by…

A

the lesser wing of the sphenoid as it surrounds the optic canal

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4
Q

Base of the orbit is formed by…

A

maxilla, frontal, and zygomatic

Note: the margin of the orbit is thickened for support and protection

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5
Q

Floor of the orbit is formed by…

A

maxilla, zygomatic, and palatine

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6
Q

Medial wall of orbit is formed by…

A

maxilla, ethmoid, and lacrimal

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7
Q

Lateral wall of orbit is formed by…

A

greater wing of sphenoid and zygomatic

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8
Q

Roof of orbit is formed by…

A

frontal

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9
Q

Where do orbital fractures typically occur?

A

At the sutures, because the margin is so thickened

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10
Q

When an orbital blowout occurs the medial wall, inferior wall, and roof of the orbit are commonly involved.

A

Damage to the floor results in bleeding into the maxillary sinus. The inferior rectus muscle can trapped causing diplopia. Fat is displaced causing enophthalmos.

Damage to the medial wall causes continuity with the ethmoidal and sphenoidal air sinuses.

Damage to the roof will cause continuity with the anterior cranial fossa

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11
Q

Exophtalmos can indicate a tumor?

A

Tumors in the air sinuses, middle cranial fossa, and infratemporal fossa can erode into the orbit and cause exophtalmos

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12
Q

Name the 6 foramina found in the orbit and what they transmit.

A

Supraorbital fissure - superior ophtalmic v., CN III, IV, V1, and VI

Optic Canal - CN II and opthalmic artery

Infraorbital fissure - Inferior ophthalmic v., infraorbital avn., and zygomatic nn.

Anterior/Posterio ethmoidal foramina - anterior and posterior ethmoidal avn.

Nasolacrimal canal - nasolacrimal duct

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13
Q

What is the periorbital fascia?

A

Lines the orbit and is continuous with the periosteal dura at the superior orbital fissure and optic canal

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14
Q

What are the check ligaments?

A

Attach to the medial and lateral walls of the orbit and the eye to prevent excessive adduciton or abduction of the eye. Also prevent posterior retraction of the eye by the rectus muscles.

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15
Q

What is the fascial sheath of the eyeball?

A

Surrounds the eyeball external to the sclera. Continuous with the fascia of the extraoccular eye muscles. Separates the eye from the orbital fat

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16
Q

The eyeball is composed of skin, connective tissue, muscle, and the tarsal plate. What is the tarsal plate?

A

The tarsal plate is a dense CT section providing support to the eyelid. Medial and lateral palpebral ligaments connect the tarsi to the medial and lateral walls of the orbit

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17
Q

What is the orbital septum?

A

A fibrous membrane connecting the tarsi to the orbital margin. Prevents periorbital fat from leaving the orbit.

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18
Q

What is the innervation of orbicularis oculi? What happens with impairment of this nerve?

A

CN VII. Lower eye lid will fall resulting in inability to fully close eye and dryness

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19
Q

Levator palpebrae muscle (Action, innervation, and impairment of innervation)

A

Elevates the upper eye lid
CN III
Loss of CN III will result in ptosis

Note: the superior tarsal portion is innervated sympathetically

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20
Q

What is horner’s syndrome and associated manifestation of the eye?

A

Loss of sympathetic innervation to the head which commonly presents with ptosis due to loss of superior tarsal portion of levator palpebrae superioris

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21
Q

Define palpebral conjunctiva, bulbar conjunctiva, conjunctival sac, and conjunctival fornices

A

Palpebral conjunctiva - epithelium of internal eyelid
Bulbar conjunctiva - epithelium of the outer sclera
Conjunctival sac - the space between the two conjuntivas which opens to the palpebral fissure
Conjunctival fornices occur superiorly and inferiorly where the two conjunctivas are continuous.

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22
Q

Describe the lacrimal apparatus (Location and function)

A

Located in the superolateral portion of the orbit. A complex tubuloalveolar gland which secretes lacrimal fluid into the conjunctival sac to lubricates the sclera and cornea.

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23
Q

How is lacrimal fluid drained?

A

Fluid flows through the lacrimal papillae with punctum to the lacrimal canaliculi. These drain to the lacrimal sac and eventually the nasal cavity via the nasolacrimal duct.

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24
Q

What two structures compose the external fibrous tunic?

A

Sclera - tough, opaque covering of the posterior 5/6 of the eye. Provides support for the globe and attachment of EOM.

Cornea - avascular, dehydrated covering of the anterior 1/6 of the eye. Provides most of the refraction for vision. Highly innervated with pain receptors

Note: Neovacularization of the cornea occurs secondary to hypoxia

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25
Q

What is the choroid and its function?

A

A highly vascularized, loose CT layer deep to the sclera which provides vascular support to the sclera and external most retina. Contains melanocytes which produce pigment to absorb excess light.

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26
Q

What is the iris and its function?

A

A structure which controls the aperature of the pupil and therefore the amount of light which enters the eye. Parasympathetic innervation via CN III causes constriction of the sphincter pupillae and constriction of the pupil. Sympathetic innervation of the dilator pupillae dilates the pupil.

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27
Q

What is the funciton of the ciliary processes and ciliary mm.?

A

The ciliary processes are responsible for the secretion of aqueous humor into the posterior chamber and serve as attachment for the zonular fibers from the lens. The ciliary mm. are innnervated to contract parasympathetically. Contraction of these muscles causes the ciliary body to elongate and the zonular fibers to lose tension allowing for near focus. Lack of stimulalion causes these muscles to relax.

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28
Q

CN II forms from which cells?

A

ganglion cells found in the inner layer of the retina

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29
Q

What is the ora serrata?

A

The scalloped border between the neuronal and non-neuronal retinal epithelium.

30
Q

What is the optic disk?

A

The area where the optic nerve and central retinal artery enter the eye. This causes a blind spot.

31
Q

What is the macula lutea and what is found at its center?

A

yellow pigmented zone lateral to the optic disk. Contains the fovea centralis, the site of greatest visual acuity.

32
Q

Describe the blood supply of the retina.

A

The neuronal portion of the retina is supplied by the central retinal artery, while the pigmented retinal epithelium and photoreceptor cells are supplied by the choroid of the uvea.

33
Q

What is retinal detachment?

A

Separation of the outer layers of the retina from the choroid cutting off metabolic support. Must be corrected promptly.

34
Q

What s presbyopia?

A

Hardening of the lens causing loss of accomodation

35
Q

What is cataracts?

A

aggregation of proteins of the lens causing them to become opaque

36
Q

Describe the flow of aqueous humor

A

Flows from the posterior chamber to the anterior chamber. In the anterior chamber it flows through the trabecular meshwork into the canal of schlemm at the iridocorneal angle. The canal of schlemm is drained by the scleral vv. and eventually to the the anterior ciliary vv.

37
Q

Explain how the neural ectoderm forms the retina and optic nerve.

A

The optic vesicles form from the forebrain ectoderm and evaginate on themselves to form optic cups. As they travel anteriorly they form an optic stalk and pull along the cranial dura. On the ventral surface of the optic stalk lies the choroid fissure which transmits the hyaloid vessels.

38
Q

What are the embryologic origins of the lens?

A

Surface ectoderms form the lens placode, then lens vesicles, and finally the lens.

39
Q

The vascular and fibrous layers of the eye form from which type of embryologic tissue?

A

Mesenchyme

40
Q

What do the two layers of the optic cup form?

A

The inner layer will form the neural layers of the retina. The outer layer forms the RPE.

41
Q

How does CN II form?

A

Nerve fribers of the retina will migrate through the choroid fissure to reach the brain.

42
Q

What is congenital retinal detachment?

A

When the nerual and pigmented layers of the retina fail to fuse?

43
Q

How do the iris and ciliary body develop?

A

The optic cup contributes the inner portion of these structures, but no neural tissue is present. The outer portion is formed by the vascular mesenchyme surrounding the optic cup.

44
Q

What is the iridopupillary membrane and what happens if it fails to degenerate?

A

The iridopupillary membrane is a vascular structure which separates the anterior and posterior chambers. Failure of this to degenerate results in congenital pupillary atresia.

45
Q

What is coloboma?

A

Failure of the choroid fissue to close. Can affect the retina.

46
Q

What is congenital aphakia

A

agenesis of the lens placode

47
Q

Ophthalmic artery
Where does it come from?
What is its course to the orbit?
What are it’s eleven branches and what do they supply?

A

Branch of the internal carotid artery which enter the orbit through the optic canal.

Central retinal artery - pierces the sheath of CN II to gain the retina, but doesn’t supply photoreceptor cells or RPE
Short ciliary aa. - pierce the sclera posteriorly to supply the choroid.
Long ciliary aa. - pierce the sclera anteriorly to supply the ciliary body and iris
Anterior ciliary aa. - also supply the iris and ciliary body
Lacrimal artery - supplies the lacrimal gland and lateral eyelid
Supraorbital a. - supplies forehead and scalp
anterior and posterior ethmoidal aa.
Supratrochlear a. - supplies forehead and scalp
Medial palpebral a. - supplies the medial eyelid
Dorsal nasal a. - dorsum of nose

48
Q

How can increased intracranial pressure cause blindness or papilledema?

A

Increase in intracranial pressure can cause compression of the optic sheath because it is continuous with the dura. Compression of CN II or the central retinal artery will cause blindness. Compression of the central retinal vein will cause papilledema.

49
Q

Name the six motion of the eyeball

A

Elevations, depression, adduciton, abduction, extortion, and intortion

50
Q

Medial rectus (Action, innervation, and integrity testing)

A

Adducts the eye
CN III
Eye held in abduction

51
Q

Lateral Rectus (Action, innervation, and integrity testing)

A

Abducts the eye
CN VI
Eye held in adduction

52
Q

Superior rectus (Action, innervation, and integrity testing)

A

Elevates, adducts and intorts
CN III
loss of elevation when eye is abducted

53
Q

Inferior rectus (Action, innervation, and integrity testing)

A

Depresses, adducts, and extorts
CN III
Loss of depression when eye is abducted

54
Q

Superior oblique (Action, innervation, and integrity testing)

A

depresses, abducts and intorts
CN IV
loss of depression when eye is fully adducted

55
Q

Inferior oblique (Action, innervation, and integrity testing)

A

elevates, abducts, and extorts
CN III
loss of elevation when fully adducted

56
Q

What do the inferior and superior divisions of CN III supply?

A

Superior division - GSE to levator palpebrae superioris and superior rectus mm.

Inferior division - GSE to inferior rectus, medial rectus, and inferior oblique mm. GVE-P to the ciliary ganglion.

57
Q

What are the clinical manifestations of occulomotor palsy?

A

Ptosis, loss of accomodation, eye abducted and depressed, pupils dilated, and diplopia.

58
Q

What does CN IV innervate and how does this palsy present?

A

Innervates superior oblique m. Palsy presents with diplopia because the eye is adducted and elevated.

59
Q

What does CN VI innervate and how does this palsy present?

A

Innervates lateral rectus m. Palsy presents with diplopia due to the eye being adducted.

60
Q

Nasociliary nerve (Comes from where and branches)

A

Branch of CN V1 (Ophthalmic nerve) which supplies the sensory root to the ciliary ganglion, short ciliary nn., long ciliary nn., anterior/posterior ethmoidal nn., and infratrochlear n.

61
Q

What do each of the branches of nasociliary innervate?

A

Short ciliary nn. - arise from ciliary gang. lateral to CN II and carries post-gang. parasympa, sympa, and sensory fibers

Long ciliary nn. - arise from nasociliary n. medial to CN II. These carry post-gang sympa. and sensory fibers.

Post/ant. ethmoidal nn. - innervate the ethmoidal air cells and dura

Infratrochlear n. - provides sensory information to root of nose, eyelids, conjunctiva, and lacrimal sac

62
Q

Frontal nerve (come from where and branches)

A

Branch of CN V1. Provides the supraorbital and -trochlear nn.

63
Q

Lacrimal nerve (comes from where and branches)

A

Branch of CN V1. provides sensory and post-gang sympa/parasympa to lacrimal gland. Also sensory to lateral superior eyelid.

64
Q

Describe the parasympathetic innervation of the sphincter pupillae and ciliary muscles

A

Preganglionic cell bodies lie in the edinger-westphal nucleus and fibers travel with the occulomotor n. to the ciliary ganglion where postganglionic cell bodies are found. Fibers distribute via the short ciliary nn.

65
Q

Describe sympathetic innervation of the dilator pupillae and superior tarsal muscles

A

Preganglionic cell bodies lie in the lateral horn of T1-2. Fibers ascend the sympathetic chain to synapse on post-ganglionic cell bodies in the superior cervical sympathetic ganglion. Post-ganglionic fibers reach the ciliary ganglion by way of the internal carotid plexus and travel through the ciliary ganglion to distribute via long and short ciliary nn.

66
Q

Describe parasympathetic innervation of the lacrimal gland

A

Preganglionic cell bodies lie in the salivatory nucleus and their fibers travel with the greater petrosal n. (CN VII) to the pterygopalatine ganglion. This is where post-ganglionic cell bodies lie and their fibers run to the lacrimal gland via the zygomatic n. (V2) and lacrimal n. (V1)

67
Q

Describe the sympathetic innervation of the lacrimal gland

A

Preganglionic cell bodies lie in the lateral horn of T1-4. These fibers ascend the sympathetic chain to synapse on postganglionic bodies in the superior cervical sympathetic ganglion. Their fibers travel with the n. of vidian and then the zygomatic (V2) and lacrimal (V1) nn. to the gland.

68
Q

Describe the pupillary reflex.

A

Afferent nerve of this reflex is CN II and the efferent nerve is CN III GVE-P

69
Q

Describe the corneal reflex.

A

CN V1 provides general sensation to the cornea. When it is irritated the the orbicularis oculi will contract via CN VII.

70
Q

Describe the accomodation reflex. Which 3 events occur?

A

Afferent through CN II and efferent is CN III.

  1. ciliary mm. contract
  2. Pupils constrict
  3. Eyes adduct

Funk Anatomy - NS Exam 3 (13 decks)

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