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K-Anatomy Block 5 > Orbit > Flashcards

Orbit Flashcards

1
Q

What forms the roof of the orbit?

A

orbital plate of the frontal bone and small part of lesser wing of sphenoid bone

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2
Q

What forms the lateral wall of the orbit? What lies lateral to it?

A

Zygomatic bone and greater wing of the sphenoid. The temporal fossa lies lateral to it.

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3
Q

What forms the medial wall of the orbit? What lies medial to it?

A

frontal, lacrimal, ethmoid, and sphenoid bones. Ethmoidal air cells lie medial to it.

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4
Q

What forms the floor fo the orbit? What lies inferior to it?

A

Orbital surface of maxilla. The maxillary sinus is inferior to it.

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5
Q

What passes through the optic canal and between what two areas?

A

optic nerve (CN II) and opthalmic artery from middle cranial fossa to orbit

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6
Q

What passes through the superior orbital fissure and what areas does it connect?

A

Superior and inferior branches of the oculomotor nerve (CN III), trochlear nerve (CN IV), abducens nerve (CN VI), lacrimal, frontal, and nasociliary branches of the opthalmic nerve (CN V1) and the superior opthalmic vein from the Middle cranial fossa to orbit.

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7
Q

What passes through the inferior orbital fissure and between what two areas?

A

Orbital branches of CN V2 (zygomatic nerve and infraorbital nerve) and the infraorbital artery from PP and IT fossas to the orbit

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8
Q

What passes through the anterior and posterior ethmoidal foramina and what spaces do they connect?

A

Anterior and posterior ethmoidal nerves and vessels pass from the orbit into the ethmoid bone

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9
Q

What structures are in superior group of the superior orbital fissure (superior to the common tendinous ring)?

A

Lacrimal and frontal branches of CN V1, CN IV, and superior opthalmic vein

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10
Q

What structures are in the middle group (inside the common tendinous ring) of the orbit?

A

CN II (optic n.), opthalmic artery, superior and inferior branches of CN III (occulomotor), nasocilliary branch of opthalmic nerve (CN V1), and CN VI (abducens)

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11
Q

What structures lie inferior to the common tendinous ring in the orbit (inferior group)?

A

Inferior opthalmic vein

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12
Q

Where does the levator palpebrae superioris originate/insert?

A

origin: lesser wing of sphenoid
insert: superior tarsal plate, skin of eyelid

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13
Q

What innervates levator palpebrae superioris?

A

CN III, upper division

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14
Q

What are the actions of levator palpebrae superioris?

A

elevate upper eyelid

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15
Q

Origin/insertion of superior, inferior, medial, and lateral recti muscles?

A

origin: common tendinous ring
insert: anterior hemisphere of eyeball on respective side.

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16
Q

What innervates the superior rectus?

A

Upper division of CN III

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17
Q

What are the actions of superior rectus?

A

elevation, aDduction, intorsion

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18
Q

What innervates inferior rectus?

A

Lower division of CN III

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19
Q

What are the actions of inferior rectus?

A

depression, aDduction, extorsion

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20
Q

What innervates medial rectus?

A

Lower division of CN III

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21
Q

What are the actions of medial rectus?

A

aDduction of eyeball

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22
Q

What are the actions of lateral rectus?

A

aBduction of eyeball

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23
Q

What innervates lateral rectus?

A

CN VI (abducens)

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24
Q

What innervates superior oblique?

A

CN IV (trochlear)

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25
Q

What are the actions of superior oblique?

A

depression, aBduction, intorsion

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26
Q

Orign/insert of superior oblique?

A

Origin: body of sphenoid
insert: lateral posterior quadrant of eyeball

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27
Q

What innervates inferior oblique?

A

Lower division of CN III

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28
Q

Origin/insertion of inferior oblique?

A

Origin: medial floor of orbit, posterior to rim
Insert: lateral posterior quadrant of eyeball

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29
Q

What are the actions of the inferior oblique?

A

elevation, aBduction, extorsion

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30
Q

What muscle are you testing by asking a patient to look laterally and up? What nerve?

A

Superior rectus. Upper division of CN III

31
Q

What muscle are you testing by asking a patient to look laterally and down? What nerve?

A

inferior rectus. Lower division of CN III

32
Q

What muscle are you testing by asking a patient to look laterally? What nerve?

A

lateral recuts. CN VI (abducens)

33
Q

What muscle are you testing by asking a patient to look medially? What nerve?

A

Medial rectus. Lower division of CN III

34
Q

What muscle are you testing by asking a patient to look medially and up? What nerve?

A

Inferior oblique. Lower division of CN III

35
Q

What muscle are you testing by asking a patient to look medially and down? What nerve?

A

Superior oblique. CN IV (trochlear)

36
Q

What is miosis?

A

permanent constriction of pupil. For our purposes, caused by loss of sympathetics, leading to parasympathetic constriction of the iris sphincter

37
Q

What is anhydrosis?

A

Loss of sweating

38
Q

What is ptosis?

A

drooping of eyelid

39
Q

What is Enopthalmos?

A

movement of eyeball posteriorly into orbit.

40
Q

What is mydriasis?

A

permanent dilation of pupil

41
Q

What is mydriasis a sign of?

A

parasympathetic loss (CN III)

42
Q

What is enopthalmos a sign of?

A

sympathetic loss

43
Q

What is ptosis a sign of?

A

sympathetic loss

44
Q

What is loss of lacrimation a sign of?

A

Parasympathetic loss (CN III)

45
Q

What is anhydrosis a sign of?

A

sympathetic loss

46
Q

What is the periorbita?

A

periostial fascia that is continuous with the periostem of the IT and middle cranial fossa

47
Q

What keeps the eyeball in the anterior of the orbit instead of sinking posteriorly?

A

The pressure from the fat in the muscular cone.

48
Q

How would a pancoast tumor cause the eye to sink into the orbit posteriorly?

A

Pancoast tumors often compress the sympathetic chain in the neck, resulting in a loss of sympathetics in the head. In the orbit, there is a smooth muscle called orbitalis that covers the inferior orbital fissure and keeps the fat/fluid of the orbit at pressure, and the eyeball at the anterior. If this is compromised, pressure is lost and the eyeball recedes into the socket

49
Q

How does Horner’s syndrome cause ptosis?

A

The Superior and Inferior tarsal muscles connect to the tarsal plates. They are smooth muscle and Horner’s results from cleavage of sympathetic fibers.

50
Q

Where would an eyelash go when it is ‘stuck in your eye’?

A

Conjuctival sac

51
Q

What group are all of the nerves to the extrinsic muscles except CN IV in?

A

Middle group (inside the common tendinous ring)

52
Q

What group is CN IV in?

A

Upper group

53
Q

What does the frontal nerve become?

A

supratrochlear nerve

54
Q

What nerve runs along the medial wall of the orbit and has medial branches that enter the ethmoid bone? What are these branches called?

A

Nasocilliary nerve. Anterior and posterior ethmoidal nerves.

55
Q

What artery follows the course of nasocilliary nerve?

A

opthalmic artery

56
Q

What muscles does CN III innervate?

A

S,M, and Inf rectus as well as Inferior oblique and Levator palpebrae

57
Q

What muscles does the Superior branch of CN III innervate?

A

Levator palpebrae superioris and and superior rectus

58
Q

Do nerves that travel in the long cilliary nerve pass through the cilliary ganglion? Do those that travel in the short cilliary nerve?

A

Long cilliary is ‘longer’ and spans the gap between the nasocilliary nerve and globe (does not pass through ganglion)

Short ciliiary nerve is a branch directly off the ganglion so even nerve fibers that do not synapse in the ganglion will pass through it.

59
Q

How do parasympathetics reach the globe?

A

They travel with CN III, pass to the ciliary ganglion via a parasympathetic root, syanpse, then travel in the short cilliary nerve to reach the globe

60
Q

What do sympathetics do in the eyeball?

A

Innervate Dilator pupil

Innervate vascular smooth muscle

61
Q

What are the two ways sympathetics can reach the eye?

A
  1. Follow opthalmic artery, branch off to form sympathetic root which passes through cilliary ganglion W/O synapsing, then courses through short cilliary nerve.
  2. Hitch a ride in the nasociliiary nerve and take long ciliary nerve
62
Q

What muscles do parasympathetics innervate in the orbit?

A

Sphincter pulillae and cilliary muscle

63
Q

What is the main function of the ciliary muscle?

A

Accommodation - changing the shape of the lens for varying distances

64
Q

What will a cholenergic agonist do?

A

Block parasympathetics, therefore dilating pupil and making accomodation impossible.

65
Q

What is nasocilliary n. a branch of?

A

CN V1

66
Q

What are the three ways GSA reaches the globe?

A
  1. Sensory root from the nasociliiary nerve (V1)
  2. Nasocilliary fibers carried in the long cilliary nerve
  3. Anteior ciliary nerve fibers from the lacrimal nerve
67
Q

What provides blood supply to the retina?

A

Central retinal artery - first branch of opthalmic artery (it is the sole blood supply to the retina)

68
Q

What nerve does the opthalmic artery follow?

A

Nasocilliary nerve.

69
Q

Is the lacrimal gland on the medial or lateral side of the orbit?

A

lacrimal lateral

70
Q

What side of the orbit is the trochlea on?

A

Trochlea is medial (lacrimal lateral)

71
Q

What foramen does opthalmic artery use to enter the orbit? What else travels with it through this?

A

Optic canal. Optic nerve (CN II)

72
Q

What is the parent branch of the zygomatic artery?

A

Lacrimal artery (on the lateral side of the orbit)

73
Q

T or F: The lateral walls of the two orbits are parallel to eachother?

A

False. They are at a 90 degree angle to eachother and the medial walls are parallel and facing forward

K-Anatomy Block 5 (9 decks)

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