Applied Anatomy and Physiology of the Orbit and Eye

Question 1

What are the 3 layers of the eye?

Answer 1

Fibrous coat

Vascular coat

Sensory coat

Question 2

What makes up the fibrous coat?

Answer 2

Sclera

Cornea

Question 3

What makes up the vascular coat?

Answer 3

Choroid

Ciliary body

Iris

Question 4

What makes up the sensory coat?

Answer 4

Retina

Question 5

What are the 5 layers of the cornea?

Answer 5

1. epithelium
2. bowmans membrane
3. stroma
4. descemets layers
5. endothelium

Question 6

What is the epithelium of the cornea?

Answer 6

it is stratified squamous non-keratinised

Cells are quite flat so stratified squamous

Unlike skin it is non-keratinized

Question 7

What is bowmans membrane?

Answer 7

the basement membrane of the coreneal epithelium

epithelium are always sitting on a basement membrane

Question 8

What is the stroma?

Answer 8

it is regular arranged collagen and has no blood vessels meaning it is transpartent which is opposite to the sclera

collagen in the cornea are arranged parallel to each other and very uniform meaning light can pass through into the eye

Question 9

what is descemets layer?

Answer 9

basement membrane for the inner epithelium called the endothelium

Question 10

What is the endothelium

Answer 10

the inner epithelium which is against the aqueous humor

it is single layered unlike the outer epithelium

Question 11

Can you see the cornea?

Answer 11

not really as it is transparent

Question 12

How is the transparency of the cornea maintained?

Answer 12

1 . histologically - regular arrangement of collagen in stroma

2. no blood vessels
3. endothelium cell layer has a pump that actively keeps the aqueous humor out

Question 13

What is aqueous humor responsible for?

Answer 13

maintenance of pressure of the eyeball

Question 14

What may start ot happen if there is not enough endothelium cells?

Answer 14

aqueous humor may start to get into the cornea and it will begin to become hazy

Question 15

Does avascularity play are role in corneal transplant?

Answer 15

yes

Question 16

What is the important role of avascularity of the cornea in corneal transplant?

Answer 16

it is a benefit to surgeons

there is a lesser chance of forgein antigens from the corneal graft being recognised by the recipient, so lesser chance of a graft rejection

Question 17

What are the 2 functions of the ciliary body?

Answer 17

1. Has muscles in which help suspend the lens and helps in changing shape of lens
2. Production of aqueous humor

Question 18

Where is aqueous humor drained?

Answer 18

angle of the anterior chamber

Question 19

Once aqueous humor is at the angle of the anterior chamber, where does the aqueous humor drain?

Answer 19

goes through a trabecular meshwork which acts as a siv

drains into a tube called schlemms canal and then eventually to veins

Question 20

How many layers make up the retina?

Answer 20

10

Question 21

What supplies blood to the retina?

Answer 21

the outer layers are supplied by the choroid

the choroid has many blood vessels of different sizes which supply the outer layers of the retina with blood through diffusion

the inner layers of the retina get blood from branches of the central retinal artery

Question 22

What is A?

Answer 22

pigment epithelial layer

Question 23

What is B?

Answer 23

layer of rods and cones

Question 24

What is C?

Answer 24

nerve fibre layer

Question 25

What is the pigment epithelial layer?

Answer 25

maintains health of retinal rods and cones (nourishes retinal visual cells) Age related macular degeneration – dystrophy effecting pigment epithelial layer which leads to destruction of rods and cones

Question 26

What is the layer of rods and cones?

Answer 26

photosensitive cells they are photoreceptors responsible for sight

Question 27

What is the nerve fibre layer?

Answer 27

recieves information as an action potential and takes it to the brain joins up to form the optic nerve

Question 28

What is the fovea centralis?

Answer 28

area packed with cones so maximum visual acuity in the middle of the eye cones are a lot more sensitive to light changes than rods in the fovea centralis all the other layers are pushed to the side

Question 29

Describe the strucutre of the lens

Answer 29

Transparent crystalline biconvex structure suspended by zonules from the ciliary body can change shape (i.e. become less or more convex)

Question 30

How is the lens transparent and what can this lead to in later life?

Answer 30

For it to be transparent, it needs to be avascular This avascularity is one of the factors that predisposes it to become opaque later in life

Question 31

What is cataract?

Answer 31

lens opacification

Question 32

What are the areas infront and behind the lens called?

Answer 32

infront - anterior segment behind - posterior segment

Question 33

WHat is the mucous membrane that lines the inside of the eyelids and the sclera on the front of the eye?

Answer 33

conjunctiva

Question 34

What muscles contorl the eye lids?

Answer 34

Orbicularis oculi helps close eye levator pupillae superioris elevates the eyelid

Question 35

What helps keep the shape and supports the eyelids?

Answer 35

tarsal plate

Question 36

What do meibomian glands do?

Answer 36

Exocrine glands found along the rims of the eyelid inside the tarsal plate They produce meibum, an oily substance that prevents evaporation of the eye's tear film

Question 37

Where do tears drain?

Answer 37

into the lacrimal sac that drains into the inferior meatus in the nose

Question 38

What produces tears?

Answer 38

Lacrimal gland is lateral and above to the eye around the LPS, secretes tears onto the surface of the gland Facial nerve is responsible for secreting parasympathetic of the lacrimal gland

Question 39

What are the functions of tear film?

Answer 39

1. Keeps cornea moist, prevents drying 2. Washes away any particulate foreign bodies 3. Has antibodies and lysozymes to kill microbes 4. Smooths outer surface of cornea providing smooth surface for refraction

Question 40

What is the strutuce of tear film?

Answer 40

Layer 1: mucinous layer (~30%) overlying corneal epithelium Layer 2: aqueous layer (~69%) lies over the mucinous layer Layer 3: oily layer (\<1%) is the most superficial

Question 41

What is the process of tear film breaking up?

Answer 41

During a blink, the sharp lower border of the upper eyelid distributes the tear film evenly When eyelids are open, aqueous component of tears begin to evaporate, and oily layer comes close to the mucin layer When these 2 layers touch each other, the tear film breaks up and stimulates further blinking