Introduction to Nervous System and Anatomy of the Eye

Question 1

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

Answer 1

• Fibrous coat
• Vascular coat
• Sensory coat

Question 2

What are the 2 components of the fibrous coat?

Answer 2

• Cornea

- Sclera

Question 3

What are the 3 components of the vascular coat?

Answer 3

• Ciliary body
• Iris
• Choroid

Question 4

What part of the eye is considered the sensory coat?

Answer 4

Retina

Question 5

What part of the eye is transparent?

Answer 5

Cornea

Question 6

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

Answer 6

• Aqueous humor

- Vitreous humor

Question 7

What are the 5 layers of the cornea?

Answer 7

• Epithelium
• Bowman’s membrane
• Stroma
• Descemet’s layer
• Endothelium

Question 8

What type of epithelium is found in the cornea?

Answer 8

Stratified squamous non-keratinised epithelium

Question 9

What is Bowman’s membrane?

Answer 9

Basement membrane of corneal epithelium

Question 10

What is the stroma?

Answer 10

Regularly arranged collagen that has no blood vessels

Question 11

How thick is the endothelium of the cornea?

Answer 11

Single layer

Question 12

How is the transparency of the cornea maintained?

Answer 12

• 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

Question 13

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

Answer 13

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

Question 14

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

Answer 14

It is an immune privileged site

Question 15

What produces aqueous humor?

Answer 15

Ciliary body

Question 16

Where is the aqueous humor found in the eye?

Answer 16

Anterior segment

Question 17

Where is the vitreous humor found in the eye?

Answer 17

Posterior segment

Question 18

How is the eye divided into segments?

Answer 18

• Anterior segment in front of the lens

- Posterior segment behind the lens

Question 19

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

Answer 19

• Anterior chamber is in front of the ciliary body

- Posterior chamber is behind the ciliary body

Question 20

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

Answer 20

• 1. Pigment epithelial layer
• 2. Layer of rods and cones
• 9. Nerve fibre layer

Question 21

What is the choroid made from?

Answer 21

Fenstrated blood vessels of varying diameter

Question 22

What do the blood vessels of the choroid supply?

Answer 22

The outer layers of the retina with blood by diffusion

Question 23

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

Answer 23

Branches of the central retinal artery

Question 24

How does the fovea centralis achieve ,maximum visual acuity?

Answer 24

Packed with cones

Question 25

What is the lens?

Answer 25

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

Question 26

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

Answer 26

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

Question 27

What is lens opacification known as?

Answer 27

Cataract

Question 28

What are the 4 functions of the tear film?

Answer 28

- 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

Question 29

How can you clinically see the tear film?

Answer 29

After staining with a dye called fluorescein

Question 30

What are the 3 layers of the tear film?

Answer 30

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

Question 31

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

Answer 31

Parasympathetic (VII)

Question 32

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

Answer 32

4 seconds

Question 33

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

Answer 33

5 seconds

Question 34

How is the tear film distributed evenly?

Answer 34

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

Question 35

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

Answer 35

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

Question 36

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

Answer 36

The tear film breaks up which stimulated further blinking

Question 37

How does the eye develop?

Answer 37

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