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Neuro Week 1 > ICL 7.0: Anatomy & Imaging of the Orbit > Flashcards

ICL 7.0: Anatomy & Imaging of the Orbit Flashcards

1
Q

what’s the importance of the ethmoid bone in relation to the orbit?

A

it separates orbit from ethmoid air cells (ethmoid sinus)

so this means it’s often involved in orbital blow out fractures

there’s also small neural foramina that could allow sinusitis bacteria infections to reach the orbit….

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2
Q

which 4 bones form the medial wall of the orbit?

A
  1. lacrimal
  2. ethmoid
  3. sphenoid
  4. maxilla
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3
Q

which bones form the roof the orbit?

A
  1. frontal bone

2. lesser wing of the sphenoid bone

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4
Q

which bones form the floor of the orbit?

A
  1. maxilla
  2. zygomatic
  3. palatine
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5
Q

which bones form the lateral wall of the orbit?

A
  1. greater wing of the sphenoid

2. zygomatic bone

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6
Q

what are the foramina of the orbit?

A
  1. optic foramen
  2. superior orbital fissure
  3. inferior orbital fissure
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7
Q

what passes through the optic foramen?

A

CN 2

ophthalmic artery

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8
Q

what passes through the superior orbital fissure?

A

CN 3, 4, 6, V1 and the superior ophthalmic vein

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9
Q

what passes through the inferior orbital fissure?

A

zygomatic and infraorbital branches of V2

parasympathetic branches of VII to lacrimal gland

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10
Q

what is a pure blowout fracture of the orbit?

A

sudden blow to the eye pushes the intact globe back into the orbit

this is accompanied by a momentary increase in intraorbital pressure resulting in a fracture or blowout via the thin portion of the orbital floor aka the maxilla and resulting in herniation of periorbital contents

posterior displacement and sudden increase in intraorbital pressure may also result in concomitant fracture of the medial wall into the ethmoid air sinuses

so TLDR = maxillary and ethmoid bones are most likely to be damaged in a blowout fracture

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11
Q

what are the 2 types of orbital fat?

A
  1. intraconal fat = fat in-between the muscles of the eye

2. extraconal fat

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12
Q

what is the function of orbital fat?

A
  1. fills the orbit outside of the eye
  2. stabilizes the eyeball and provides insulation
  3. in starvation it’s lost and the eyeballs “sink in”
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13
Q

what is the annulus of zinn?

A

connective tissue that is the point of attachment for all the extraoccular eye muscles

it’s a thickening of the periosteum

aka the common tendinous ring

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14
Q

what is the periorbita?

A

dense connective tissue membrane that serves as an attachment site for muscles, tendons, and ligaments and is a support structure for the blood supply to the orbital bones

it is loosely attached to the orbital bone but firmly attached to orbital fissures, optic foramen and it continuous with:

  1. external periosteum
  2. orbital septum
  3. fascial sheath on eye and extra-ocular muscles (EOMs)
  4. dura

slide 14 go look at the picture

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15
Q

what is the orbital septum?

A

it’s a membrane originating at the periorbita and extending into each eyelid

it acts as a barrier to the spread of infection and hemorrhage

medially, the orbital septa of the upper and lower eyelid pass behind the lacrimal sac, where they blend with fibers of the medial canthal tendon before inserting onto the lacrimal crest

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16
Q

what is periorbital cellulitis?

A

an inflammation and infection of the eyelid and portions of skin around eye

it’s found anterior to the orbital septum so it’s an infection outside the orbital septae!

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17
Q

what is orbital cellulitis?

A

inflammation of tissue posterior to orbital septum usually due to spread of infection from adjacent sinuses or via blood

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18
Q

what are the symptoms of orbital cellulitis?

A
  1. pain moving eye
  2. sudden loss of vision
  3. bulging of the infected eye
  4. limited movement
  5. redness and swelling of the eyelid, accompanied by pain, discharge and inability to open the eye
19
Q

which structures are located within the common tendinous ring? aka annulus of zen

A

within the optic canal:
1. optic nerve CN 2

  1. ophthalmic artery

in superior orbital fissure:
1. CN 3 and 6

  1. nasociliary (V1)
20
Q

which structures are located outside the common tendinous ring in the superior orbital fissure? aka annulus of zen

A
  1. trochlear CN 4
  2. frontal nerve (V1)
  3. lacrimal nerve (V1)
  4. ophthalmic vein
21
Q

what are the 2 types of ptosis?

A
  1. acquired

2. congenital

22
Q

what is acquired ptosis?

A

“drooping eyelids”

due to paralysis or paresis of muscles that elevate the upper eyelid

muscles involved:
1. levator palpebrae superioris

  1. superior tarsal muscle
23
Q

what is congenital ptosis?

A

poor development of the levator palpebralis muscle

24
Q

what are conjunctiva?

A

they’re opaque over posterior lid and transparent over sclera

25
Q

what is the conjunctival sac?

A

the total space posterior to closed eyelids

26
Q

what is the canthus?

A

the junction of the upper and lower eyelids

the medial canthus is separated from eyeball by triangular space called the “lacrimal lake” which contains “lacrimal caruncle”

27
Q

what is the palpebral conjunctiva?

A

if you pull down your eye lid to check for anemia, that’s your palpebral conjunctiva

it’s also the part you see if you flip your top eyelid inside out

28
Q

what is the bulbar conjunctiva?

A

the conjunctiva covering your actual eyeball

29
Q

what is the conjunctiva innervated by?

A

CN V = trigeminal nerve

  1. palpebral conjunctiva

CN V1 = upper eyelid

CN V2 = lower eyelid

  1. bulbar conjunctiva = CN V1
30
Q

what is conjunctivitis?

A

an inflammation or infection of the transparent membrane (conjunctiva) that lines your eyelid and covers the white part of your eyeball

eye looks pink or red and may have discharge

note: pink eye does not always suggest an infection…foreign body, allergy, contact lenses, etc

31
Q

what are the 3 components of the lacrimal fluid?

A
  1. lipid
  2. aqueous
  3. mucin
32
Q

what are the characteristics of lacrimal fluid?

A

it has the pH of physiological saline = 7.4

it also contains lysozyme which is a bactericidal enzyme used as a defense mechanism

33
Q

what is the function of lacrimal fluid?

A
  1. smooth irregularities of cornea and creates even surface of good optical quality
  2. provides O2 to corneal surface
  3. removes metabolic waste from cornea
  4. microbial defense of eye
34
Q

what is the lacrimal gland?

A

it’s located in shallow bony fossa in superior-lateral orbit

the lacrimal fluid that comes from moistens, lubricates, oxygenates cornea

35
Q

what is the lacrimal apparatus pathway?

A
  1. lacrimal gland (in lacrimal fossa)
  2. lacrimal ducts
  3. superior fornix of conjunctival sac
  4. across eye surface
  5. lacrimal lake
  6. lacrimal canaliculi
  7. lacrimal sac
  8. nasolacrimal duct
  9. inferior nasal meatus
36
Q

what are the 6 extra-ocular muscles?

A

Horizontal rectus

  1. Medial rectus (MR)
  2. Lateral rectus (LR)

Vertical rectus

  1. Superior rectus (SR)
  2. Inferior rectus (IR)

Oblique

  1. Superior oblique (SO)
  2. Inferior oblique (IO)

ALL rectus muscles originate from the common tendinous ring

37
Q

what are the extra-ocular muscles innervated by?

A
  1. lateral rectus = CN 6
  2. superior oblique = CN 4

all other muscles are CN 3!

38
Q

which eye muscles help you look up?

A

Superior rectus (SR)

Inferior oblique (IO)

39
Q

which eye muscles help you look down?

A

Inferior rectus (IR)

Superior oblique (SO)

40
Q

what is the function of torsional eye movements?

A

they compensate for head tilt!

they’re what maintains the visual horizon when your head or neck tilts and they rotate the eyes in the direction opposite from the head/neck tilt

41
Q

which eye muscles are involved in intorsion aka medial rotation?

A
  1. superior rectus

2. superior oblique**

42
Q

which eye muscles are involved in extorsion aka lateral rotation?

A
  1. inferior rectus

2. inferior oblique**

43
Q

what are the arteries of the orbit?

A

the internal carotid artery gives off a branch that is the ophthalmic artery

there’s other stuff but we don’t need to know it (:

44
Q

what are the 3 main veins of the orbit?

A
  1. superior ophthalmic vein
  2. inferior ophthalmic vein
  3. infra-orbital vein

the veins are MUCH bigger in comparison to the orbital arteries

Neuro Week 1 (9 decks)

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