Introduction to Nervous System and Anatomy of the Eye Flashcards

1
Q

What are the 3 layers of the eye from outside in?

A
  • Fibrous coat
  • Vascular coat
  • Sensory coat
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2
Q

What are the 2 components of the fibrous coat?

A
  • Cornea

- Sclera

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3
Q

What are the 3 components of the vascular coat?

A
  • Ciliary body
  • Iris
  • Choroid
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4
Q

What part of the eye is considered the sensory coat?

A

Retina

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5
Q

What part of the eye is transparent?

A

Cornea

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6
Q

What are the 2 types of humor found in the eye?

A
  • Aqueous humor

- Vitreous humor

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7
Q

What are the 5 layers of the cornea?

A
  • Epithelium
  • Bowman’s membrane
  • Stroma
  • Descemet’s layer
  • Endothelium
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8
Q

What type of epithelium is found in the cornea?

A

Stratified squamous non-keratinised epithelium

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9
Q

What is Bowman’s membrane?

A

Basement membrane of corneal epithelium

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10
Q

What is the stroma?

A

Regularly arranged collagen that has no blood vessels

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11
Q

How thick is the endothelium of the cornea?

A

Single layer

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12
Q

How is the transparency of the cornea maintained?

A
  • Histologically by the regular arrangement of collagen in stroma
  • No blood vessels
  • Endothelium cell layer has a pump that actively keeps the aqueous humor out
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13
Q

Why is the avascularity of the cornea a benefit to surgeons when performing corneal transplants?

A

It means there is a lesser chance of foreign antigens from a corneal graft being recognised by the recipient so lesser chance of a graft rejection

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14
Q

What does the avascularity of the cornea lead researchers to believe?

A

It is an immune privileged site

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15
Q

What produces aqueous humor?

A

Ciliary body

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16
Q

Where is the aqueous humor found in the eye?

A

Anterior segment

17
Q

Where is the vitreous humor found in the eye?

A

Posterior segment

18
Q

How is the eye divided into segments?

A
  • Anterior segment in front of the lens

- Posterior segment behind the lens

19
Q

How is the anterior segment of the eye divided into chambers?

A
  • Anterior chamber is in front of the ciliary body

- Posterior chamber is behind the ciliary body

20
Q

What are the 3 important layer of the retina and choroid to remember?

A
    1. Pigment epithelial layer
    1. Layer of rods and cones
    1. Nerve fibre layer
21
Q

What is the choroid made from?

A

Fenstrated blood vessels of varying diameter

22
Q

What do the blood vessels of the choroid supply?

A

The outer layers of the retina with blood by diffusion

23
Q

Where do the inner layers of the retina get blood from?

A

Branches of the central retinal artery

24
Q

How does the fovea centralis achieve ,maximum visual acuity?

A

Packed with cones

25
Q

What is the lens?

A

Transparent, crystalline biconvex structure which is suspended by zonules from the ciliary body. It can change shape.

26
Q

What is one of the factors that can predispose the lens to becoming opaque in later life?

A

For it to be transparent it needs to be avascular therefore avascularity is one of the predisposing factors

27
Q

What is lens opacification known as?

A

Cataract

28
Q

What are the 4 functions of the tear film?

A
  • Keeps cornea moist, prevents drying
  • Washes away any particulate foreign bodies
  • Has antibodies and lysozymes to kill microbes
  • Smooths outer surface of cornea providing smooth surface for refraction
29
Q

How can you clinically see the tear film?

A

After staining with a dye called fluorescein

30
Q

What are the 3 layers of the tear film?

A
  • Mucinous layer (~30%) overlying corneal epithelium
  • Aqueous layer (~69%) over the mucinous layer
  • Oily layer (<1%) is the most superficial
31
Q

What is responsible for the innervation of the secretion of tears into the conjunctival sac?

A

Parasympathetic (VII)

32
Q

How long from blinking does it take for the tear film to break up?

A

4 seconds

33
Q

How long after blinking does it take for ocular discomfort to occur?

A

5 seconds

34
Q

How is the tear film distributed evenly?

A

During a blink, the sharp lower border of the upper eyelid distributes the tear film evenly

35
Q

What happens to the tear film when the eyes are open?

A

Aqueous component of tears begin to evaporate and oily layer comes close to the mucin layer

36
Q

What happens when the mucin layer touches the oily layer of the tear film?

A

The tear film breaks up which stimulated further blinking

37
Q

How does the eye develop?

A

Optic vesicles grow outwards from diencephalic part of the neural tube towards surface ectoderm