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Head and Neck > Week 5 - Orbit anatomy > Flashcards

Week 5 - Orbit anatomy Flashcards

1
Q

Which bone makes the superior orbital ridge?

A

-Frontal

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2
Q

Which bone makes the inferior orbital ridge?

A

-Zygomatic and maxilla

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3
Q

Name the boundaries of the orbit

A
  • Apex = optic canal
  • Superior = Frontal and Sphenoid
  • Lateral = zygomatic and sphenoid
  • Medial = ethmoid, maxillary, lacrimal and sphenoid
  • Inferior = maxillary and zygomatic
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4
Q

Which boundary of the orbit is the thinnest?

A

-Medial

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5
Q

What runs through the optic canal?

A
  • Optic nerve

- Ophthalmic artery

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6
Q

Name the foramina of the bony orbit

In which bone do they lie?

A
  • Optic canal
  • Superior orbital fissure
  • Inferior orbital fissure
  • Sphenoid
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7
Q

What runs through the superior orbital fissure?

A
  • CNIII
  • CNIV
  • CNV1
  • CNVI
  • Superior ophthalmic vein
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8
Q

What is a blow out fracture? How does it present? How is it treated?

A
  • Fracture to the inferior border of the orbit causing inferior rectus (and other muscles) to herniate into maxillary sinus
  • Patient will have a history of blow to the eye and will be unable to look up
  • Steroids and antibiotics (sometimes requires surgery)
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9
Q

Why is it crucial the iris is able to contract and dilate?

A
  • Allow different amounts of light into the eye
  • Dilates in the dark to allow more light to enter
  • Contracts in the light to prevent too much light from entering and damaging the retina
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10
Q

What is the function of the lens?

A

-Focus the light into the retina

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11
Q

Name the 3 layers of the eyeball and their constituents

A
  • Outer fibrous -> Cornea, Sclere
  • Middle vascular -> Ciliary body, Iris, choroid
  • Inner -> retina, macula
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12
Q

Why is there a blind spot in the eye?

A

-optic disk where optic nerve enters

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13
Q

What is visual acuity?

A

-Clarity of vision

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14
Q

What is the ciliary body?

A
  • Part of the eye which includes the ciliary muscle.

- Accommodation (involving contracting/relaxing the iris) and produces/resorps aqueous humor

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15
Q

What is the retina?

A

-Inner most layer of the eye which contains photoreceptors (cones and rods) which transmit chemical and electrical impulses down optic nerve

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16
Q

What is the sclera?

A

-White of the eye -> Protective fibrous layer of the eye containing collagen and elastic fibres

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17
Q

What is the choroid?

A
  • Vascular layer of the eye containing connective tissue which lays between retina and sclera
  • Functions to provide oxygen and nourishment to the outer layers of the eye
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18
Q

What is the macula?

A

-Oval shaped pigmented area of retina which is the place of most visual acuity

19
Q

What is accommodation?

A

-Changes in lens shape (more convex or concave) to focus light from objects at different distances in order to maintain a clear image

20
Q

What is the cornea? Why is it avascular

A
  • Transparent front part of the eye which covers the iris and the lens
  • Refracts light to generate optical power
  • Avascular so it is transparent
21
Q

What is the iris?

A

-The coloured part of the eye which contracts and relaxes to adjust the amount of light reaching the lens

22
Q

What is retinal detachment? Why can it occur?

A
  • Trauma to the face can cause the retina to become detached from the eyeball causing flashes/blurring in unilateral vision.
  • Can occur as the retina and choroid have different embryological origins-> initially separated by intraretinal space but enentually fuse together -> leaves weak area
23
Q

Can retinal detachment always be fixed?

A

-There is a time sensitive window to fix it

24
Q

Why is photophobia experienced in meningitis?

A

-Optic nerve is a brain tract (outpouching of brain) and thus is surrounded by meninges (pia, arachnoid and dura mater)

25
Q

Describe the segments/chambers of the eye

A
  • Eyeball split into anterior and posterior segments -> posterior segment is behind the lens
  • Anterior segment separated further into anterior and posterior chambers -> divided by ciliary body
26
Q

What is the function of the aqueous humor of the eye?

A

-Provide oxygen and nutrients to the cornea and lens as it is avascular

27
Q

What produces the aqueous humor of the eye and how does it circulate?

A
  • Produced by ciliary body to fill both the anterior and posterior chambers of the eye
  • Flows out through trabecular meshwork in the anterior chamber of the eye
28
Q

What is open angle glaucoma?

A
  • Condition where the trabecular meshwork becomes blocked abd excess fluid accumulates between the cornea and the iris
  • Increases intraorbital pressure causing compression of optic nerve
  • Progressive painless vision loss
29
Q

What is a cataract?

A

-Hardening and flattening of the lens producing a reduced ability to focus vision and a glare as light scatters across the lens

30
Q

Name the muscles of the orbit and their nerve supply

A
  • Superior oblique -> Trochlear nerve
  • Lateral rectus -> abducens
  • Inferior oblique, inferior/superior/medial rectus, levator palpabrae superioris -> Oculomotor
31
Q

What happens in a trochlear nerve palsy?

A

-Patient unable to look down and in (lost superior oblique)

32
Q

What happens if inferior oblique is damaged?

A

-Cannot look up and in

33
Q

Where does the central retinal artery come from?

A

-Ophthalmic artery

34
Q

Describe what happens in a central retinal artery occlusion

A
  • Loss of blood supply to retinal of eye except for at macula as it receives its blood supply from choroid
  • Retina looks pale everywhere except macula
35
Q

Describe the venous drainage of the eye

Why is this clinically relevant?

A
  • Central retinal vein -> Superior ophthalmic vein -> cavernous sinus
  • Means eye infection can track to brain
36
Q

What is papiloedema?

A

-Optic disk swelling caused by increased intracranial pressure which slows venous drainage from the eye -> usually bilateral

37
Q

How does central retinal vein occlusion differ from central retinal artery occlusion?

A
  • Slow painful loss of vision -> will be rapid in artery

- Several haemorrhages seen on eyeball rather than pale

38
Q

Explain Lacrimal drainage

A

-Lacrimal gland -> lacrimal sac -> nasolacrimal duct -> inferior meatus

39
Q

What is the purpose of the eyelid?

A

-Protect from injury, excessive light and dryness

40
Q

Describe the conjunctiva

A
  • Stratified columnar epithelium which covers inside of the eyelids and sclera which helps to lubricate the eye
  • Palpebral layer covers eyelid
  • bulbar layer covers sclera
41
Q

What is a meibomian cyst?

A

-Painless swelling of eyelid due to infection in the tarsal gland

42
Q

What is a sty?

A
  • Infection of the cillary gland causing painful swelling of the eyelid
  • Usually caused by staph
43
Q

What muscle opens the eyelid?

A

-Levator Palpabrae Superioris

superior tarsal

44
Q

Which muscle closes the eyes?

A

-Orbicularis oculi

Head and Neck (18 decks)

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