Applied Anatomy and Physiology of the Orbit and the Eye

Question 1

What are the 3 coats of the eye ball?

Answer 1

Fibrous coat

Vascular coat

Sensory coat

Question 2

label the diagram

Answer 2

Question 3

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

Answer 3

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

Question 4

What is the classification of the epithelium of the cornea?

Answer 4

Stratified squamous non-keritinised

Question 5

What is the Bowman’s membrane?

Answer 5

Basement membrane of corneal epithelium

Question 6

What is the stroma?

Answer 6

Regularly arranged collagen

Question 7

Are there any blood vessels in the stroma?

Answer 7

No blood vessels

Question 8

How many layers form the endothelium of the cornea?

Answer 8

Single layer (normally 2500 cells/mm²)

Question 9

How is transparency maintained in the cornea?

Answer 9

Histologically by the regular arrangement of collagen in stroma

No blood vessels

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

Question 10

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

Answer 10

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

Question 11

how do aqueous humour work/drain?

Answer 11

Cornea

Question 12

This image shows the histology of the eyeball, what is B?

Answer 12

Sclera

Question 13

This image shows the histology of the eyeball, what is C?

Answer 13

Sclemm’s canal

Question 14

This image shows the histology of the eyeball, what is D?

Answer 14

Trabecular network

Question 15

What is Schlemm’s canal?

Answer 15

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

Question 16

What is the trabecular meshwork in the eyeball responsible for?

Answer 16

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

Question 17

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

Answer 17

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

Question 18

What is the choroid?

Answer 18

Vascular layer of the eye lying between the retina and sclera

Question 19

What is the choroid made up of?

Answer 19

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)

Question 20

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

Answer 20

Inner - branches of central retinal artery

Outer - Diffusion from choroid

Question 21

Where in the retina is maximum visual activity?

Answer 21

Fovea centralis

Question 22

What is the retina?

Answer 22

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

Question 23

What is the lens?

Answer 23

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

Question 24

What shape is the lens?

Answer 24

Biconvex

Question 25

What is the lens suspended from and by?

Answer 25

Suspended from the ciliary body by zonules

Question 26

Can the lens change shape?

Answer 26

Yes, can become more or less convex

Question 27

Why is the lens avascular?

Answer 27

For it to be transparent

Question 28

What is lens opacification called?

Answer 28

Cataract

Question 29

What are functions of the tear film?

Answer 29

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

Question 30

How can you see the tear film clinically?

Answer 30

Staining with a dye called fluorscein

Question 31

What are the 3 layers of the tear film?

Answer 31

Mucinous layer (about 30%)

Aqueous layer (about 69%)

Oily layer (about 1%), most superficial

Question 32

What does the mucinous layer of the tear film overly?

Answer 32

Corneal epithelium

Question 33

Explain the tear film dynamics?

Answer 33

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

Question 34

What causes the secretion of tears into the conjunctival sac?

Answer 34

Parasympathetic innervation from CN VII

Question 35

Explain the process of blinking?

Answer 35

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