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Human Structure Block 3 FA22 > Orbit > Flashcards

Orbit Flashcards

1
Q

Where is the orbit located?

A

Inferior to frontal sinus
Lateral to ethmoid air cells
Superior to maxillary sinus

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2
Q

What happens if bony sinuses continue to become inflammed?

A

Erosion into the orbit can occur causing visual disturbances (dipoplia)

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3
Q

What are the bones of the orbit?

A

Margin: frontal, zygomatic, and maxillary

Medial: lacrimal, ethmoid, frontal and sphenoid (lesser wing)

Lateral: Zygomatic, zygomatic process, and sphenoid (greater wing)

Floor: Maxilla, zygomatic, and palatine

Roof: orbital plate of frontal bone

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4
Q

Superior Orbital Fissure separates what bone?

A

Greater and Lesser wings of the sphenoid bone

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5
Q

The inferior orbital fissure communicates with what?

A

Infratemporal fossa

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6
Q

What shape is the orbit in?

A

Cone shaped with apex pointing posterior

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7
Q

What degree are the eyes on the long (visual) axis of the eyeball to the long axis of the oribit (orbital axis) when looking anterior?

A

23 degrees

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8
Q

What is position of rest (in reation to the eye)?

A

All extraocular muscles are relaxed

Divergent with visual axis in line with orbital

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9
Q

Attachment, function, and innervation of Levator Palpebrae Superioris

A

Attachment: Lesser wing of Sphenoid to upper eyelid
Function: opens the eyelid
Innervation: Superior division of oculomotor nerve (CNIII)

*the small tarsal muscle on the superior eyelid is innervated by sympathetic of carotid plexus

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10
Q

What does the tendinous ring contain?

A

Optic canal and lower part of inferior orbital fissure

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11
Q

What is the fibrous sheath continuous around the muscles of the eye called?

A

Fibromuscular cone

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12
Q

The fibromuscular cone is filled with what?

A

Fat and optic nerve

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13
Q

All muscles of the eye (except inferior oblique) attach where?

A

Near the common tendinous ring and the scleral coat of the eye

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14
Q

What are the movements of the eye?

A

Elevation
Depression
Adduction
Abduction
Incyclotorsion
Excyclotorsion

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15
Q

What are the extraocular mucles?

A

Lateral Rectus
Medial Rectus
Superior Rectus
Inferior Rectus
Superior Oblique
Inferior Oblique

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16
Q

What is the function(s) of the Lateral Rectus?

A

Purely abducts

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17
Q

What is the function(s) of the Medial Rectus?

A

Purely Adducts

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18
Q

What allows for focusing on a near object?

A

Convergence of the gaze where eyes adduct

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19
Q

What is the function(s) of the Superior Rectus?

A

Elevation, Incyclotorsion, and adduction

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20
Q

What is the function(s) of the Inferior Rectus?

A

Depression, Excyclotorsion, and Adduction

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21
Q

What is the function(s) of the Superior Oblique?

A

Incyclotorsion, depression, and abduction

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22
Q

Where does the superior oblique msucle sit?

A

Along medial wall and through the trochlea where the tendon then sits posterior to equator and later to axis of rotation

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23
Q

What is the function(s) of the Inferior Oblique?

A

Excyclotorsion, elevation, abduction

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24
Q

If I wanted to look straight up, what muscle would I be using?

A

Superior Rectus and inferior oblique

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25
Q

If I wanted to look straight down, what muscle would I be using?

A

Inferior rectus and Superior Oblique

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26
Q

If I wanted to look left, what muscle would I be using?

A

Left lateral rectus and right medial rectus

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27
Q

If I wanted to look right, what muscle would I be using?

A

Right lateral rectus and left medial rectus

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28
Q

If I wanted to look up and to the right, what muscle would I be using?

A

Right inferior oblique and left superior rectus

29
Q

If I wanted to look up and to the left, what muscle would I be using?

A

Left inferior oblique and right superior rectus

30
Q

If I wanted to look down to the right, what muscle would I be using?

A

Right superior oblique and left inferior rectus

31
Q

If I wanted to look downa nd to the left, what muscle would I be using?

A

Left superior oblique and right inferior rectus

32
Q

What are the innervations of the extraocular eye muscles

A

LR6 SO4 (all else 3)

33
Q

All of the extraocular nerves are considered what?

A

General somatic efferent

34
Q

What is the pathway for CN 3 in the orbit?

A

Moves through the superior orbital fissure (within the tendinous ring) before splitting into a superior and inferior division

35
Q

What does the superior and inferior division of CN3 innervate?

A

Superior: Levator palpebrae superioris and superior rectus

Inferior: Inferior rectus, Medial rectus, and inferior oblique

36
Q

If you wanted to test the lateral rectus muscle in patient, what would you ask them to do? What is this also testing for?

A

Please look laterally (abduct). (CN VI)

37
Q

If you wanted to test the medial rectus muscle in patient, what would you ask them to do? What is this also testing for?

A

Please look medially (adduct). (CN III)

38
Q

If you wanted to test the Superior Rectus muscle in patient, what would you ask them to do? What is this also testing for?

A

Pleas abduct your eye. Then try to elevate the eye.
(CN III; Superior Division)

You want the gaze axis parallel to the line of pull

39
Q

If you wanted to test the inferior oblique muscle in patient, what would you ask them to do? What is this also testing for?

A

Please adduct the eye and then elevate it
(CN III; Inferior Division)

Visual gaze is parallel to line of pull

40
Q

If you wanted to test the Superior Oblique muscle in patient, what would you ask them to do? What is this also testing for?

A

Please adduct the eye and then depress it.
(CN IV)

Visual gaze is parallel with line of pull

41
Q

If you wanted to test the Inferior Rectus muscle in patient, what would you ask them to do? What is this also testing for?

A

Please Abduct the eye and then depress it.
(CN III; Inferior Division)

Visual gaze is parallel to line of pull

42
Q

Lacrimal fluid production is under what ANS control?

A

Parasympathetic

43
Q

What is the pathway of fluid flow from the lacrimal gland?

A
  1. Lacrimal Gland
  2. Flows medially across the eye
  3. Lacrimal Punctum
  4. Canaliculi (superior and inferior)
  5. Common Canaliculi
  6. Lacrimal Sac
  7. Nasolacrimal duct
  8. Inferior Meatus of the nose
44
Q

What does lacrimal fluid do?

A

Protect and moisten the cornea
Traps particles

45
Q

Describe the pathway of parasympathetic innervation of the lacrimal gland

A
  1. Nervus Intermedius (carried by CN 7)
  2. Greater Petrosal Nerve
  3. Nerve to Pterygoid Canal
  4. Pterygopalatine ganglion (synapse here)
  5. Zygomatic nerve (From maxillary division V2)
  6. Communication branch to Lacrimal nerve
  7. Lacrimal nerve of V1
  8. Lacrimal Gland
46
Q

The ophthalmic artery comes from what?

A

Internal carotid a.

47
Q

Where does the ophthalmic artery enter the orbit?

A

Optic canal

48
Q

What is the first branch of the ophthalmic a.

A

First branch: central artery of retina

49
Q

The central retinal artery branches into what structures?

A

Superior and inferior branches which branch into superior/inferior nasal and temporal branches

50
Q

What does the central retinal artery provide blood to?

A

retinal ganglion cells whose axons carry information back to brain via optic nerve

51
Q

The medial branch of the ophthalmic artery branches into what arteries?

A

Supraorbital (for scalp)
Posterior ethmoidal (for posterior ethmoidal air cells)
Anterior ethmoidal (for ethmoidal and frontal air sinuses)
Medial palpebral (for eyelids)
Terminal branches: Supratrochlear (for forehead) and Dorsal nasal (for dorsum of nose)

52
Q

The lateral branch of the ophthalmic artery branches into what?

A

Lacrimal artery (for lacrimal gland and eyelids)
Long and short posterior ciliary arteries (for choroid)

Some branches that supply the front of eye are the anterior ciliary arteries

Short supply back of eyeball

53
Q

Where do veins of the orbit drain?

A

Superior and inferior ophthalmic vein which communicate with the cavernous sinus and pterygoid plexus

54
Q

What is the consequence of occlusion of the central artery of the retina and why?

A

Transient visual loss (amaurosis fugax). The central artery is the end artery and there is no collateral circulation in the retinal area

55
Q

How does CN III enter the orbit?

A

Divides into 2 nerves above and below the nasocilliary nerve within the cone

56
Q

Where does CN VI enter the orbit?

A

Within the fibrous ring

57
Q

Where does CN IV enter the orbit?

A

Superior to fibrous ring (outside the muscular cone) and medial

58
Q

Describe the parasympathetic innervation of the eye

A
  1. Inferior Branch of CN III carries preganglionic parasympathetic from Edinger-Westphal nucleus (midbrain)
  2. Synapses at ciliary ganglion (from nasociliary nerve (V1))
  3. Short ciliary nerves carry the postganglionic fibers to the back of eyeball
  4. Innervates the sphincter pupillae (reducing amount of light) and ciliary muscle (decreases tenson on zonular fibers allowing near vision)
59
Q

All sensory nerves in the orbit come from what?

A

Ophthalmic division of trigeminal nerve (V1)

60
Q

What are the branches of V1 in the orbit?

A

Frontal Nerve: divides into supraorbital and supratrochlear supply forehead and scalp

Lacrimal: Supply skin of eyelids but also carries some post-parasympathetic fibers to lacrimal gland

Nasociliary: Branches into 2 long ciliary, posterior/anterior ethmoidal, and infratrochlear

61
Q

Difference between Long and Short Ciliary Nerves

A

Long: Branch of nasociliary that carry Post-sympathetic fibers coming from superior cervical ganglion to dilator pupillae (GSA)

Short: From ciliary ganglion that carry post-parasympathetic fibers to ciliary muscles and sphincter pupilae (does contain post-sympathetic through ciliary ganglion but does not synapse)

62
Q

The ciliary ganglion transmits parasympathetic fibers to which structure via the short ciliary nerves?

A

Ciliary muscles and sphincter pupillae

63
Q

What causes an orbital floor fracture?

A

Increased intraocular pressure from posterior displacement of eye or a direct blow to the infraorbital rim

64
Q

If the orbital floor is fractured, what is the main concern?

A

Entrapment of inferior rectus muscle and fat (can cause ischemia)

65
Q

Who is more likely to have entrapment of inferior rectus muscles during an orbital floor fracture?

A

Children due to the linear pattern of fracture (flexibility in bones) leading to a trap-door fracture

66
Q

What are the signs of Orbital Floor Fractures?

A
  1. Orbital dystopia: eye on affected side is lower due to entrapped inferior rectus muscle and fat
  2. Enophthalmos: Eye is displaced posteriorly due to prolapse of tissue into maxillary sinus
  3. Injury to Infraorbital nerve from V1: Decreased sensation along cheek and upper lip
67
Q

What can you ask a patient to see if they have an orbital floor fracture?

A

Look up and down (you want to see the limitations caused by entrapment of inferior rectus muscle)

68
Q

What is Trochlear Nerve Palsy and what do you see?

A

Paralysis of superior oblique muscle

Hypertropia: eye turned up in primary position

Patients will adopt a contralateral head tilt and chin tuck

69
Q

What is Strabismus?

A

Misaligned eyes

Human Structure Block 3 FA22 (9 decks)

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