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Matt's Block 06 - Neuro block > W21-L1: Contents of the Orbit > Flashcards

W21-L1: Contents of the Orbit Flashcards

1
Q

What forms the supra-orbital margin?

A

The frontal bone

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2
Q

What forms the infro-orbital margin?

A

Zygomatic bone laterally and maxialla medially

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3
Q

Which bones form the roof of the orbit?

A

Frontal bone, lesser

wing of sphenoid

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4
Q

Which bones form the floor of the orbit?

A

Maxilla,

zygomatic, palatine

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5
Q

Which bones form the lateral wall of the orbit?

A

Zygomatic, greater

wing of sphenoid

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6
Q

Which bones form the medial wall of the orbit?

A

Maxilla, lacrimal bone, ethmoid, body of sphenoid

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7
Q

Which bone of the orbit is often fractured?

A

Lacrimal and ethmoid bones as they are very thin, so medial wall

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8
Q

What are the three layers of they eye?

A

Outermost: Sclera and cornea
Middle layer: Vascular (Uvea)
Inner layer: Neuronal

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9
Q

How much of the eyeball does the sclera cover?

A

5/6ths

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10
Q

What is the function of the sclera?

A

-Maintains the shape of the globe, offering resistance to
internal and external forces.
-Provides attachments for the EOMs

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11
Q

Why is the sclera so tough?

A

The collagen and the arrangement which is not parallel, instead its in whirls

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12
Q

What is the cornea?

A

Structure that is continuous with the sclera and covers the anterior 1/6th of the eye

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13
Q

What is the function of the cornea?

A 
Principal refracting component of
the eye (~60% of refraction)
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14
Q

Why is the cornea optimum for vision?

A

Avascular and transparent

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15
Q

How many layers are there in the cornea?

A

Five

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16
Q

What is the epithelium layer in the cornea?

A

Mucus membrane

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17
Q

What is the stroma composed of in the cornea?

A

Collagen that is neatly arranged so its transparent

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18
Q

What is the role of the endothelium in cornea?

A

Controls water balance in the eye

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19
Q

How is the collagen arranged in the cornea?

A
  • Uniform in diameter and evenly spaced
  • run parallel to each other in bundles called lamellae
  • adjacent lamellae lie at angles to each other
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20
Q

What does the varying scleral opacity depend on?

A
  • Composition of the stroma
  • Hydration
  • Size and distribution of the collagen
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21
Q

What happens if you lose only the epithelium in the cornea?

A

It heals with no scar

22
Q

What happens if you get stroma injury in the cornea?

A

Loss of ordered collage and transparency, a scar if in the cornea

23
Q

What is the anterior chamber angle?

A
  • Junction between iris and cornea

- Where aqueous humour drains out of eye.

24
Q

What are the key structures in the anterior chamber angle?

A
  • Cornea
  • Trabecular meshwork
  • Canal of Schlemm
  • Ciliary body
25
Q

What makes up the uvea?

A

Iris, ciliary body and choroid

26
Q

What are some important structures in the ciliary body?

A

Ciliary processes (ciliary eptihelium) which form aqueous humour and form an attachment for ligaments of the lens

Ciliary muscle which allows us to focus (accommodation)

27
Q

What is the function of aqueous humour?

A
  • Important for maintaining the health of the lens and cornea.
  • Creates intraocular pressure.
28
Q

Where does the aqueous humour move around the eye?

A

Passes through pupil, and drains via anterior chamber angle into the venous supply.

29
Q

What are zonules?

A

ligaments that attach between cililary processes and lens.

30
Q

What does accommodation involve?

A
  1. ciliary muscle

2. Zonules that attach to lens.

31
Q

What is the most important fibres of the ciliary muscle and what innervates them?

A

Circularly fibres are the most important, they are innervated by parasympathetic fibres

32
Q

What causes expansion of lens?

A

Lack of tension due to contraction of ciliary muscles

33
Q

Presbyopia

A

Refers to the loss of accommodation with

age caused by reduction in flexibility in the lens capsule and zonules

34
Q

What is the iris?

A

The aperture of the eye

35
Q

What muscles are in the iris?

A
  • Sphincter pupillae: constricts pupil: innervated by parasymp NS.
  • Dilator pupillae: dilates pupil: innervated by Sympathetic NS
36
Q

What is the choroid?

A

The three layers of the blood vessels underneath the retina that supplies it

37
Q

Which is the most important layer of the choroid?

A

Choriocapillaris

38
Q

What are the important parts of the retina?

A
  • Optic nerve/optic disc
  • Fovea/foveola
  • Macular
  • Posterior pole
  • Orra serrata
39
Q

What is the orra serrata?

A

Edge of the retina

40
Q

What is special about the fovea?

A

High visual acuity, avascular, high density of cones and no rods

41
Q

What is the Lamina cribosa?

A
  • Band of dense connective tissue.
  • Sieve-hole that transmit nerve fibres.
  • Collagen fibres from sclera.
  • 3-10 sheets of connective tissue.
42
Q

Why is the Lamina cribosa important?

A

In disease can damage ganglions around it

43
Q

The orbit blood supply is from where?

A

From the opthalamic artery which is the first branch of the internal carotid

44
Q

What supplies the retina from the inner surface?

A

Central retinal artery, first branch of opthalamic, pierces optic nerve and fans out over the retina

45
Q

What are the ciliary arteries?

A
  • Long posterior ciliary artery
  • Short posterior ciliary artery
  • Anterior ciliary artery
46
Q

What is the path of the posterior ciliary arteries?

A

-posterior cilliary arteries pierce the globe around the
optic nerve and travel in the choroid
-if they travel short and feed head of optic nerve they
are called short, if they travel round to the front of the eye they are long

47
Q

What is the path of the anterior ciliary arteries?

A

does not pierce the globe, runs forward and supplies anterior structures

48
Q

What is the blood supply to the retina?

A

Dual blood supply to retina:

  • Central retinal artery supplies the inner retina
  • Posterior ciliary artery supplies the outer retina (photoreceptors)
49
Q

What are the eyelids?

A

transition zone between mucus and skin

50
Q

What are the two muscles of the orbit?

A
  • Orbicularis oculi

- Levator palpebrae superiosis

51
Q

What is the function of Levator palpebrae superiosis and what innervates it?

A

Elevates upper lid, innervated by CN III

52
Q

What is the function of Orbicularis Oculi and what innervates it?

A

Sphincter muscle that depresses upper lid, innervated by CN VII

Matt's Block 06 - Neuro block (48 decks)

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