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Anatomy > Eye and Orbit > Flashcards

Eye and Orbit Flashcards

1
Q

What are the walls of the orbit?

A

roof
lateral wall
medial wall
floor

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2
Q

What are the bones of the orbit?

A

frontal
ethmoid with body of sphenoid posteriorly
lacrimal
maxilla
zygomatic
lesser wing of sphenoid
greater wing of spehnoid

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3
Q

What are the openings into the orbit?

A

superior orbital fissure
optic canal
nasolacrimal canal
inferior orbital fissure

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4
Q

o

What are the contents of the superior orbital fissure?

A

abducent nerve
lacrimal branch of the ophthalmic nerve (V1)
frontal branch of the ophthalmic nerve (V1)
trochlear (IV)
superior branch of oculomotor nerve (III)
nasociliary branch of opthalmic nerve (V1)
inferior branch of oculomotor nerve (III)

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5
Q

What are the contents of a optic canal?

A

optic nerve

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6
Q

Where is the superior orbital fissure?

A

between the lesser and greater wings of sphenoid bone

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7
Q

What CN are in the superior orbital fissure?

A

CNIII, IV, VI

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8
Q

What are the contents of the orbit?

A
  1. optic nerve (CNII) with central retinal artery and vein (end/terminal artery)
  2. eyelids and lacrimal apparatus
  3. extraocular muscles
  4. eyeball
  5. retrobulbar fat in the orbit supporting the eyeball
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9
Q

What do the optic nerves form and where is it?

A

As the optic nerves enter the skull they meet & form the optic chiasm that lies just superior & anterior to the pituitary gland (tunnel vision)

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10
Q

What is tunnel vision?

A

With bitemporal hemianopsia, you lose vision in the temporal visual field of each eye. With one eye closed, the other eye will lose vision in its temporal visual field

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11
Q

What is the structure of optic nerve (CNII)?

A

dura mater
arachnoid mater
subarachnoid space
pia mater
central retinal vein
central retinal artery

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12
Q

Where do the meninges and subarachnoid space extend?

A

extend from skull along the optic nerve (CN II) to the sclera

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13
Q

What pathology can occur in the central retinal artery?

A

can become occluded due to transient causes causing amaurosis fugax that leads to painless temporary loss of vision in the affected eye

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14
Q

What can cause papilloedema?

optic disk swells

A

Raised intracranial pressure is transmitted to the meninges & subarachnoid space around the optic nerve (CN II) that slows retinal venous drainage via the central retinal vein

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15
Q

What are the layers of eyelids

A

skin
connective tissue
muscle (orbicularis oculi)
orbital septum
tarsus
conjunctiva

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16
Q

What is the orbital septum?

A

Anterior border of orbit continuous with periosteum

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17
Q

What is the space between eyelids called?

A

palpebral fissure

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18
Q

What is the role of the superior/inferior tarsus?

A

eyelid support

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19
Q

What is preseptal cellulitis?

what is it important to differentiate from?

A

▪ Infection of the skin/subcutaneous tissue (superficial layers) anterior to the orbital septum
▪ Important to differentiate from orbital cellulitis

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20
Q

What is orbital cellulitis?

what is the threat?

A

▪ Infection posterior to the orbital septum
▪ Pain on movements of the eye that are restricted along with proptosis (bulging of the eye)
▪ Threatens vision & there is risk of infection spread to cavernous sinus or meninges/brain

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21
Q

What is conjunctivitis?

A

(pink eye) Inflammation of the membrane covering the posterior surface of the eyelid & eyeball

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22
Q

What is the sensory innervation of the eyelids?

A

CN V1, V2

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23
Q

What is the arterial supply of the eyelids from?

A

via the external carotid (facial, transverse facial, superficial temporal) & internal carotid (supratrochlear, supraorbital, lacrimal) arteries

24
Q

What is venous drainage of the eyelids from?

A

veins following arteries

25
Q

What is lymphatic drainage via?

A

parotid nodes

26
Q

What are the actions of the orbicularis oculi and what is it innervated by?

A

Its actions are to close the eyelids gently (involuntary or blinking reflex; palpebral part) or tightly (voluntary; orbital part)
Innervated by the facial nerve (CN VII)

27
Q

What can malfunction of the orbicularis oculi cause?

A

may lead to sagging of the lower eyelid, leakage of tears & dry eyes with the potential for corneal ulceration

28
Q

Where is the lacrimal gland?

A

upper lateral corner of orbit

29
Q

Where are tears screted from the lacrimal gland?

A

Tears are secreted into the conjunctival sac & continually washed across the eye by blinking of the eyelids

30
Q

How do tears drain?

A

Tears form a tiny lake at the medial angle of the eye where the lacrimal caruncle lies
Tears drain via punctae to canaliculi, to lacrimal sac, to nasolacrimal duct & to inferior nasal meatus

31
Q

What is the parasympathetic supply of the lacrimal gland?

path

A
  • Preganglionic parasympathetic fibres from facial nerve (CN VII) nervus intermedius
  • Travel in greater petrosal nerve & then nerve of pterygoid canal
  • Arrive in the pterygopalatine (‘hay fever’) ganglion
  • Postganglionic parasympathetic fibres hitch-hike with zygomatic branch of CN V2 to reach the lacrimal gland
32
Q

What are the extraocular muscles?

A

superior oblique
levator palpebrae superioris
superior rectus
medial rectus
lateral rectus
inferior oblique
inferior rectus

from top to bottom

33
Q

What is the innervation of each extraocular muscle?

A

superior oblique (IV)
levator palpebrae superioris (III)
superior rectus (III)
medial rectus (III)
lateral rectus (VI)
inferior oblique (III)
infeior rectus (III)

LR6 SO4 R3

34
Q

What action does each extraocular muscle carry out?

A

Lateral Rectus: Abduction (moves the eye outward, away from the nose).

Medial Rectus: Adduction (moves the eye inward, toward the nose).

Superior Rectus: Intorsion (twisting of the top of the eye towards the nose)

Inferior Rectus: Extorsion (rotates the top of the eye away from the nose)

Superior Oblique: Intorsion

Inferior Oblique: Extorsion

35
Q

What is the function of the levator palpebrae superioris?

A

raising and retracting the upper eyelid

36
Q

What does the oculmotor nerve supply and carry?

A
  • Supply extraocular muscles as indicated in the previous diagram
  • Supply levator palpebrae superioris
  • Carry parasympathetics for pupil constriction & accommodation
  • Carry sympathetics to supply the smooth muscle component of levator palpebrae superioris (also termed as the superior tarsal muscle)
37
Q

What can injury of CNIII cause?

A

remove the parasympathetic pupil constriction leading to a dilated pupil with ptosis (complete loss of levator palpebrae superioris) & the eye is turned downwards & outwards (superior oblique & lateral rectus are intact)

38
Q

What can CNIII palsy cause?

A

eaves the superior oblique & lateral rectus unopposed to turn the eye downwards & outwards (divergent squint) along with ptosis (drooping of superior eyelid)

39
Q

What can compress CNIII?

what does the CNIII lie between?

A

CN III also passes between the posterior cerebral & superior cerebellar arteries before lying close to the posterior communicating artery
Aneurysms of those vessels may compress CN III

40
Q

What is ptosis?

A

drooping of superior eyelid

41
Q

What muscles are unaffected by CNIII palsy

what actions can they still carry out?

A

CN IV (trochlear) supplies the superior oblique to turn the eye downwards & laterally

CN VI (abducens) supplies the lateral rectus to abduct the eye outwards

42
Q

What does CN IV palsy cause?

A

superior oblique muscle weak, and makes looking down (going downstairs & reading books) difficult

43
Q

What does CNVI palsy out?

A

CN VI palsy leaves lateral rectus weak, and therefore the muscles supplied by CN III, CN IV will pull the eye inward causing (convergent squint )

44
Q

What is the relation of CNIII, IV, VI to the cavernous sinus?

A

pass anteriorly in the cavernous sinus or its wall to enter the orbit through the superior orbital fissure

45
Q

What plexus do the CNIII, IV and VI pass close to?

A

sympathetic fibres forming the plexus on the internal carotid artery & may pick up sympathetic fibres

46
Q

What is the general structure of the eyeball?

A

the anterior & posterior chambers are separated by the iris but communicate via the pupil & contain aqueous humour

47
Q

What are the layers of the eyeball?

A

The sclera forms the outer fibrous layer (replaced by the cornea anteriorly), then is the vascular choroid layer followed by the retina which is the innermost layer

48
Q

What is the thicker part of the retina?

A

the optic part of the retina

49
Q

What is the choroid and what does it continue as?

A

The choroid (vascular layer of the eye) continues as the ciliary body, which forms a supportive ring around the lens and iris.

50
Q

What does the ciliaris muscle in the ciliary body do?

under what nervous control is this?

A

When the ciliary muscle contracts (under parasympathetic control, Cranial Nerve III), it makes the ring smaller, relaxes the suspensory ligaments, and allows the lens to become rounder. This helps in focusing on close objects (accommodation).

51
Q

What muscles does the iris contain, what are they innervated by and what is their actions?

A

Sphincter pupillae (controlled by parasympathetic system, CN III, Edinger-Westphal nucleus): constricts the pupil.

Dilator pupillae (controlled by the sympathetic system): dilates the pupil.

52
Q

What is the aqueous humour secreted by and what does it reabsorb/drain to?

A

Produced by the ciliary body.
Drains through the scleral venous sinus (canal of Schlemm).

53
Q

What is the function of the aqueous humour?

A

keeps your eye inflated and provides nourishment

54
Q

What is the cause of glaucoma and how can drugs help?

A

Caused by increased pressure if drainage is blocked. Drugs that constrict the pupil can help by pulling open the drainage channels

55
Q

Are the zonular fibres tense or relaxed when the ciliary muscles contact under parasympathetic innervation?

A

relaxed

56
Q

Why does the lens become more spherical during parasympathetic stimulation?

A

This increased curvature/thickness allows the lens to bend light more sharply (refract), focusing it onto the retina for close-up vision.

57
Q

What is the function of the scleral venous sinus (canal of Schlemm)?

A

to collect the aqueous humor from the anterior chamber of the eyeball and deliver it to the veins of the eyeball

Anatomy (13 decks)

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