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Gross Anatomy > Exam 4 Orbit > Flashcards

Exam 4 Orbit Flashcards

1
Q

Orbit​

  • Apex
  • Base
  • Superior border
  • Inferior border
  • Medial border
  • Lateral border
A
  • Apex: Lesser wing of sphenoid
    • Contains optic foramen/canal
  • Base: Orbital margin (rim)
    • Contains supraorbital foramen, Infraorbital foramen
  • Superior border: Frontal lobe and lesser wing of sphenoid
  • Inferior border: Maxilla, zygomatic, and palantine bones
    • Contains inferior orbital fissure, maxillary sinus
  • Medial border: Ethmoid, maxilla, lacrimal, and sphenoid bones
    • Contains ethmoid air cells, anterior/posterior ethmoidal foramina, nasolacrimal canal
  • Lateral border: Zygomatic bone and greater wing of sphenoid
    • Contains superior orbital fissure
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2
Q

In a blow out fracture or persistent infection, which parts of the orbital are most susceptible to damage and why?

A
  • Medial wall and floor because they are the thinnest aspects of the orbital.
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3
Q

Lacrimal gland

  • Where is it located?
  • Where does it secrete tears?
    • What makes up this space?
  • What path do tears take when they drain?
A
  • Located in superolateral aspect of the orbit
  • Secretes tears into conjunctival sac
    • Made up of palpebral conjunctiva and bulbar conjunctiva
  • Pathway: Tears swept medially by blinking of eyelids
    • Drain into punctum on medial aspect of eyelid
    • Drain from punctum to nasolacrimal duct that opens into the nasal cavity
    • Drains into nasal cavity under the inferior concha on the lateral wall.
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4
Q

Tarsal plates

  • How are they anchored to orbital margin?
  • What is the function of the tarsal glands?
A
  • Anchored by medial and lateral palpebral ligaments
  • Tarsal glands secrete fatty substance that prevents eyelids from sticking together when they are closed.
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5
Q

Levator palpebrae superioris muscle

  • Action
  • Innervation
  • Blood Supply
A
  • Action: Raises upper eyelid
  • Innervation: Oculomotor (CN III)
  • Blood Supply: Ophthalmic artery
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6
Q

Superior tarsal muscle

  • Action
  • Innervation
  • What can happen from a lesion of the nerve supplying this muscle?
A
  • Action: Maintins tone of the eyelid (involuntary muscle back up for when levator palpebrae superioris is fatigued or damaged).
  • Innervation: Sympathetic fibers traveling with frontal nerve
  • Ptosis can occur from lesion of superior cervical ganglion (or Horner’s syndrome)
    • Horner’s Syndrome: disruption of sympathetics to eye and area around eye
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7
Q

Rectus muscles

  • Origin
  • Attachment
  • Action
  • Innervation
  • Blood Supply
A
  • ALL rectus muscles originate from common tendinous ring
  • ALL rectus muscles attach to anterior 1/2 of eyeball
  • Superior Rectus
    • ​Action: Elevates, adducts, medially rotates eyeball
    • Innervation: Oculomotor (CN III)
    • Blood Supply: Ophthalmic artery
  • Inferior Rectus
    • ​Action: Depresses, adducts, laterally rotates eyeball
    • Innervation: Oculomotor (CN III)
    • Blood Supply: Ophthalmic artery
  • Lateral Rectus
    • ​Action: Abducts eyeball
    • Innervation: Abducent (CN VI)
    • Blood Supply: Ophthalmic artery
  • Medial Rectus
    • ​Action: Adducts eyeball
    • Innervation: Oculomotor (CN III)
    • Blood Supply: Ophthalmic artery
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8
Q

Oblique Muscles

  • Origin
  • Attachment
  • Action
  • Innervation
  • Blood Supply
A
  • Both attach to posterior 1/2 of eyeball
  • Superior Oblique:
    • Origin: Body of sphenoid
    • Action: Abducts, depresses, and medially rotates eyeball
    • Innervation: Trochlear (CN IV)
    • Blood Supply: Ophthalmic artery
  • Inferior Oblique:
    • Origin: Anterior floor of orbit lateral to nasolacrimel canal
    • Action: Abducts, elevates, and laterally rotates eyeball
    • Innervation: Oculomotor (CN III)
    • Blood Supply: Ophthalmic artery
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9
Q

Movements of the eye

Which muscles perform what action?

A
  • Abduction: Lateral rectus
  • Adduction: Medial rectus
  • Elevation: Superior rectus, inferior oblique
  • Depression: Inferior rectus, superior oblique
  • Intortion (rotate eye toward nose): Superior oblique and superior rectus
  • Extortion (rotate eye away from nose): Inferior oblique and inferior rectus
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10
Q

Assessing the action of complementary muscle pairs of extraocular muscles and testing the integrity of the cranial nerves.

  • What must the visual axis be aligned with for each muscle?
  • How do you test each muscle?
A

Visual axis must be aligned with Line of Pull of muscle being tested.

Test for lesion of CN III unless stated otherwise.

  • Testing Lateral and Medial Rectus:
    • Eye in level forward gaze
    • Lateral Rectus: Abduct eye (test for CN VI lesion)
    • Medial Rectus: Adduct eye
  • Testing Superior and Inferior Rectus:
    • Pupil abducted 22.5˚ from midsagittal plane
    • Superior Rectus: Abduct and look up
    • Inferior Rectus: Abduct and look down
  • Testing Superior and Inferior Oblique:
    • Visually axis maximally adducted (cross-eye)
    • Superior Oblique: Adduct and look down (testing for CN IV lesion)
    • Inferior Oblique: Adduct and look up
    • Since superior and inferior obliques also intort/extort respectively, CN IV lesion would cause inferior oblique to be unopposed, resulting in diplopia (double vision) with extortion
      • Characteristic head tilt to decrease double vision
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11
Q

What composes each layer of the eye?

  • External fibrous layer
  • Middle vascular layer
  • Internal retinal layer
A
  • External fibroud layer
    • Sclera: posterior 5/6 of eye; opaque
    • Cornea: anterior 1/6 of eye; transparent
  • Middle vascular layer
    • Choroid: adherent to retina and terminates at ciliary body
    • Ciliary body: connects choroid to iris
      • Ciliary muscle: parasympathetic innervation; contracts to change thickness of lens
    • Iris: contractile colored diaphragm anterior to lens
      • Sphincter pupillae: parasympathetic; constricts pupil
      • Dilator pupillae: sympathetic; dilates pupil
  • Internal retinal layer:
    • Optic disc: where optic nerve enters eye, blind spot (no receptors, just fibers)
    • Macula lutea: Contains fovea centralis (most acute area of vision)
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12
Q

What are the refractive media light must pass through before reaching retina?

A
  • Cornea: Transparent and avascular (long healing periods for abrasions)
    • Continuous with sclera at sclerocorneal junction
  • Aqueous humor: Clear watery fluid in anterior & posterior chambers of eyeball
    • Made by ciliary processes
    • Drained through iridio-corneal angle to circular venous canal of Schlemm
  • Lens: Transparent biconvex structure within transparent capsule
    • Curvature altered by contraction of suspensory ligament of lens (off ciliary bodies)
    • Accommodation is reflex that allows us to view objects a short distance away from eye
  • Vitreous body: Jelly-like matrix filling space b/w lens and retina
    • Not continually replaced
    • “Floaters” are cellular debris from vitreous body
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13
Q

What can clinically happen in relation to the lens if:

  • CN III is damaged?
  • There is a loss of transparency?
A
  • If CN III is damaged, muscles responsible for accommodation cannot contract and thus accommodation is lost.
  • Loss of transparency = cataracts
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14
Q

Branches of ophthalmic artery and what they supply

A
  • Lacrimal artery: supplies lacrimal gland
  • Central artery of retina: supplies retina
  • Ciliary arteries: supply structures within the eyeball
  • Supraorbital artery: exits orbit via supraorbital notch
  • Anterior and posterior ethmoidal arteries: supply ethmoid air cells and nasal cavity
  • Dorsal nasal artery: supplies dorsum of nose
  • Supratrochlear artery: terminal branch of ophthalmic artery
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15
Q
  • What are they veins of the orbit?
  • Where to they exit the orbit?
  • What do they drain into?
A
  • Superior and inferior ophthalmic veins
    • Arise form supraorbital and angular veins
    • Pass trhough superior orbital fissure
    • Drain into cavernous sinus
  • Central vein of retina
    • Travels with central artery of retina
    • Drains into cavernous sinus
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16
Q
  • What are the branches of V1 (Ophthalmic division of trigeminal nerve)?
  • What do they supply?
A
  • Frontal nerve: Divides into supratrochlear and supraorbital nerves
    • Provide sensory innervation to forehead and anterior scalp
  • Lacrimal nerve: Sensory innervation to lacrimal gland, conjunctiva of the eye, skin of the upper eyelid
  • Nasociliary nerve: Divides into:
    • Ant/Post ethmoidal nerve: supply ethmoidal air cells, nasal cavity, and external aspect of nose
    • Long ciliary n: Sympathetics to dilator pupillae m
    • Short ciliary n: Sympathetics to dilator pupillae m
      • Parasympathetics to sphincter pupillae and ciliaris mm.
17
Q

What does Oculomotor (CN III) supply?

A
  • Superior division: Levator palpebrae superioris, superior rectis
  • Inferior division: Medial rectus, inferior rectus, inferior oblique

[SO4(LR6)]3

18
Q

Pathway parasympathetics take to lacrimal gland.

A
  • Superior salivary nucleus ->
  • Greater petrosal nerve ->
  • Synapse in Pterygopalatine ganglion ->
  • Postganglionics travel through zygomatic nerve ->
  • Join Lacrimal nerve ->
  • Lacrimal gland
19
Q

What does the trochlear nerve (CN IV) supply?

A

Motor innervation to superior oblique muscle.

20
Q

What does the abducens nerve (CN VI) supply?

A

Motor innervation to lateral rectus muscle.

21
Q

What does the optic nerve supply?

What does it pass through?

A
  • Sensory innervation to eye
  • Passes through optic canal

Gross Anatomy (21 decks)

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