CHAPTER 14- Ocular anatomy and physiology Part 2 (1)

Question 1

What is the crystalline lens?

Answer 1

The crystalline lens provides refractive power and allows the eye to focus on objects at different distances.

Question 2

What 3 layers does the crystalline lens consist of?

Answer 2

1- An elastic capsule covering the entire surface

2- A simple epithelium underneath this

3- The bulk of the lens is made of elongated cells (lens fibres)

Question 3

What are lens fibres?

Answer 3

Lens fibres are long hexagonal cells that run from the front to the back surface of the lens.

Question 4

Adjacent lens fibres are joined by what and what does it allow?

Answer 4

Adjacent lens fibres are joined by gap junctions to allow the flow of nutrients.

Question 5

What do the elastic properties of the capsule ensure?

Answer 5

Ensures that the lens’s natural state is thick and round.

Question 6

The lens is suspended within a ring of fibrous strands called…

Answer 6

Zonules

Question 7

What are zonules composed of?

Answer 7

Composed of cysteine- rich fibrillin, giving them elasticity.

Question 8

Where do the zonules run along?

Answer 8

The zonule fibres run along the ciliary body and attached to the pars plana.

Question 9

When the ciliary muscle contracts, what happens to the diameter of the ciliary body and what does this allow?

Answer 9

The diameter of the ciliary body decreases.

This allows the zonule fibres to go lax (relax).

This results in the lens becoming thicker and rounder.

Question 10

What happens to the lens when the ciliary muscle is contracted?

Answer 10

The lens becomes wider and more curved, increasing its refractive power.

This allows the eye to focus on near objects (accommodation)

Question 11

Is the vitreous chamber the largest of the three chambers?

Answer 11

Yes

Question 12

Where is the vitreous chamber located?

Answer 12

Located behind the lens and in front of the retina.

Question 13

What is the vitreous chamber filled with?

Answer 13

This is filled with vitreous humour

Question 14

What is the vitreous humour?

Answer 14

A clear gel, which is more viscous than aqueous.

Viscous- much more substance to it.

Question 15

What does the vitreous humour consist of?

Answer 15

It is 99% water, with just a few cells as well as some salts, sugars, plus a network of collagen fibrils extend throughout to make it gel- like.

Question 16

What is the main function of the vitreous humour?

Answer 16

Provides support for the eyeball.

Question 17

With age, what happens to the vitreous humour?

Answer 17

With age, collagen fibres degrade and the vitreous starts to liquify.

The fibres holding the surrounding membrane to the retina can break, potentially leading to small floaters or even complete vitreous detachment.

Question 18

What is the retina?

Answer 18

Receives information and sends it to the brain through the optic nerve.

Question 19

What does the retina line?

Answer 19

The retina lines the back of the eye

Question 20

What is the retina composed of?

Answer 20

It is composed of neurons, gilia, epithelial cells, and blood vessels, etc.

Question 21

How are the layers in the retina arranged?

Answer 21

Back to front

Question 22

What are the photoreceptors in the retina and what do they do?

Answer 22

The photoreceptors are the sensory receptors that convert the optical image into nervous potentials.

Question 23

Cones and rods are designed for what levels?

Answer 23

Cones are designed for high light levels

Rods are designed for low light levels

Question 24

How does the retinal pigment epithelium (RPE) support the photoreceptors?

Answer 24

It transports nutrients to the photoreceptor cells and removes waste products from photoreceptor cells.

Question 25

The retina is made up of 5 main types of neurons:

Answer 25

1- Photoreceptors 
2- Horizontal cells
3- Bipolar cells
4- Amacrine cells 
5- Ganglion cells