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Nervous System > Applied Anatomy and Physiology of the Orbit and the Eye > Flashcards

Applied Anatomy and Physiology of the Orbit and the Eye Flashcards

1
Q

What are the 3 coats of the eye ball?

A

Fibrous coat

Vascular coat

Sensory coat

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2
Q

What are the different layers in the histology of the cornea?

A

1) Epithelium
2) Bowman’s membrane
3) Stroma
4) Descemet’s layer
5) Endothelium

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3
Q

What is the classification of the epithelium of the cornea?

A

Stratified squamous non-keritinised

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4
Q

What is the Bowman’s membrane?

A

Basement membrane of corneal epithelium

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5
Q

What is the stroma?

A

Regularly arranged collagen

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6
Q

Are there any blood vessels in the stroma?

A

No blood vessels

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7
Q

How many layers form the endothelium of the cornea?

A

Single layer (normally 2500 cells/mm2)

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8
Q

How is transparency maintained in the cornea?

A

Histologically by the regular arrangement of collagen in stroma

No blood vessels

Endothelium layer having a pump that actively keeps the aqueous humor out

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9
Q

What is the advantage of the cornea having no blood vessels for a corneal graft?

A

Lesser chance of foreign antigens being recognised by the recipient so lesser chance of the graft being rejected

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10
Q

What is Schlemm’s canal?

A

Circular lymphatic like vessel in the eye that collects aqueous humor from the anterior chamber and delivers it into the episcleral blood vessels

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11
Q

What is the trabecular meshwork in the eyeball responsible for?

A

Responsible for draining the aqueous humor from the eye via the anterior chamber

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12
Q

What is the histology of the retina (and choroid)?

A

1) Pigment epithelial layer
2) Layer of rods and cones
3) Outer limiting membrane
4) Outer nuclear layer
5) Outer plexiform layer
6) Inner nuclear layer
7) Inner plexiform layer
8) Ganglion cell layer
9) Nerve fibre layer
10) Inner limiting membrane

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13
Q

What is the choroid?

A

Vascular layer of the eye lying between the retina and sclera

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14
Q

What is the choroid made up of?

A

Fenestrated blood vessels of varying diameter which supply the outer layers of retina with blood by diffusion (inner layers get blood from branches of central retinal artery)

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15
Q

How do the inner and outer layers of the retina get blood?

A

Inner - branches of central retinal artery

Outer - Diffusion from choroid

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16
Q

Where in the retina is maximum visual activity?

A

Fovea centralis

17
Q

What is the retina?

A

Thin layer of tissue that lines the back of the eye on the inside

18
Q

What is the lens?

A

Transparent, biconvex structure in the eye that along with the cornea helps to refract light to be focused on the retina

19
Q

What shape is the lens?

A

Biconvex

20
Q

What is the lens suspended from and by?

A

Suspended from the ciliary body by zonules

21
Q

Can the lens change shape?

A

Yes, can become more or less convex

22
Q

Why is the lens avascular?

A

For it to be transparent

23
Q

What is lens opacification called?

A

Cataract

24
Q

What are functions of the tear film?

A

Keeps cornea moist, prevents drying

Washes away any particulate foreign bodies

Has antibodies and lysosomes to kill microbes

Smooths outer surface of cornea providing smooth surface for refraction

25
Q

How can you see the tear film clinically?

A

Staining with a dye called fluorscein

26
Q

What are the 3 layers of the tear film?

A

Mucinous layer (about 30%)

Aqueous layer (about 69%)

Oily layer (about 1%), most superficial

27
Q

What does the mucinous layer of the tear film overly?

A

Corneal epithelium

28
Q

Explain the tear film dynamics?

A

Teat film breaks up a second before ocular discomfort and a few seconds before a blink

29
Q

What causes the secretion of tears into the conjunctival sac?

A

Parasympathetic innervation from CN VII

30
Q

Explain the process of blinking?

A

1) Sharp lower border of the upper eyelid distributes the tear film evenly
2) When the eyelids open aqueous ocmponent of tears behin to evaporate and oily layer comes close to the mucin layer
3) When these 2 layers touch the tear film breaks up and stimulates further blinking

Nervous System (48 decks)

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