Lab 3 Eye dissection

Question 1

What does the lateral rectus muscle do?

Answer 1

Moves the eye outwards, away from the nose (abduction)

Question 2

What does the medial rectus muscle do?

Answer 2

This moves the eye inwards, towards the nose (adduction)

Question 3

What does the superior rectus muscle do?

Answer 3

Moves the eye Upwards (Elevation) Rotates the top of the eye towards the nose (intorsion) Moves the eye inward (adduction)

Question 4

What does the inferior rectus muscle do?

Answer 4

Moves the eye downwards (depression) Rotates the top of the eye away from the nose (extorsion) Moves the eye inward (adduction)

Question 5

What does the superior oblique muscle do?

Answer 5

Rotates the top of the eye towards the nose (intorsion) Moves the eye downwards (depression) Moves the eye outwards (abduction)

Question 6

What does the inferior oblique muscle do?

Answer 6

Rotates the top of the eye away from the nose (extorsion) Moves the eye upwards (elevation) Moves the eye outwards (abduction)

Question 7

What is the retractor bulbi and why don’t humans have one?

Answer 7

Retractor bulbi is a muscle that pulls the eye back into the orbit. Primates don’t have it as they don’t hang their heads for prolonged periods of time.

Question 8

Why is there such a lot of adipose tissue around the eye?

Answer 8

It is there to protect/cushion the eye upon impact and for thermal insulation.

Question 9

What does the ora serrata represent, and why does it have this name?

Answer 9

The ora serrata represents a junction between the ciliary body and the retina. It has its name because of its serrated edges.

Question 10

What type of tissue is vitreous humour and what is its function?

Answer 10

It is a type of connective tissue.

Its functions include helping push the retina to the back of the eye, maintaining shape and providing nutrients. ( as we can’t have any blood vessels in the inner eye as this would stop light getting to the retina).

Question 11

What is the main tissue type found in the retina?

Answer 11

pigmented epithelial cells

Question 12

What physical optical phenomenon is responsible for the ‘eyeshine’ produced by the tapetum lucidum?

Answer 12

The tapetum lucidum sits behind the retina and acts as a mirror, reflecting back photons of light that was not initially absorbed by the retina, giving the retina a “second chance” to detect the light. This improves their night vision and is what gives rise to the phenomenon of “eyeshine” often seen when taking photographs of animals.

Question 13

Why is the tapetum lucidam sometimes unevenly distributed?

Answer 13

if the original light is minimum or uneven then that’s what will reflect back

Question 14

What sort of epithelium is RPE (retinal pigment epithelium)?

Answer 14

Simple cuboidal

Question 15

What are the dimensions of a typical RPE (retinal pigment epithelium) cell?

Answer 15

20 microns

Question 16

What is the shape of a typical RPE cell and why?

Question 17

What accounts for the spherical clear area in the centre of some of the RPE (retinal pigment epithelia)?

Answer 17

the nucleus that does not contain any melanin

Question 18

What pigment makes the RPE cells appear brown and what is it’s function?

Answer 18

melanin

• absorbs light and improves image quality (black box effect - it absorbs any scattered light)

Question 19

Which lens surface is more curved?

Answer 19

the posterior side is more curved and it is flatter on the anterior side

Question 20

Label these parts of the eye.

Answer 20

he ora serrata (4),

the pars plana – flat portion (5)

pars plicata – folded portion (6)

the iris (7)

the lens (3).

Question 21

What feature distinguishes the pars plana and pars plicata?

Answer 21

Pars plana is a flattened part of the ciliary body in the uvea, it is the middle layer of the 3 layers that compromise the eye- i.e. its between the plars plicata and ora serrata.

Pars plicata is the most anterior portion of the ciliary body of the eye. It has has a stipped and folded appearance closest to the lens.

Question 23

The iris and ciliary body appear black. What pigment is responsible for this? What is the function of this pigmentation?

Answer 23

Black pigment - melanin

Black due to melanocytes

function: blocks light from passing through the iris to the retina, restricting it to the pupil = BLACK BOX EFFECT to prevent light from scattering

Question 24

What is the limbus?

Answer 24

where the sclera and cornea merge

Question 25

What is drained at the filtration angle?

Answer 25

intraocular fluid or aqueous humour

Question 26

What pathological condition results from inadequate drainage?

Answer 26

Glaucoma

Question 27

What is the structural difference between the corneal and sclera connective tissue fibres and what is the functional consequence of this?

Answer 27

In the eye, the corneal stroma is made of regularly arranged collagen fibres. This is what makes it transparent

Sclera collagen fibres = irregular -> this makes the structure opaque

Question 28

Label this drawing and flip for the answers.

Answer 28

Question 29

label these parts of the eye

Answer 29