Visual System

Question 1

What protects the eye?

Answer 1

1. Bony socket in skull
2. Eyelids: shutters to protect from environmental hazards
3. Eyelashes: trap fine, airborne debris before falling into the eye
4. Tears: lacrimal glands and conjunctiva lubricate, cleanse and act as bacteriocide.

Question 2

What are the three tissue layers that enclose the eye?

Answer 2

1. Sclera/cornea,
2. choroid/ciliarybody/iris
3. Retina

Question 3

What is the sclera?

Answer 3

Tough outer layer of connective tissue, forms visible white part of the eye

Question 4

What is the cornea?

Answer 4

Anterior, transparent layer continuous with sclera that allows passage of light rays

Question 5

What is the choroid?

Answer 5

Middle layer underneath sclera which contains blood vessels that nourish retina and contain melanin under retina for absorption of light

Question 6

What is the ciliary body?

Answer 6

Continuous tissue of muscle from choroid layer that controls the curving and flattening of the lens.

Question 7

what is the retina?

Answer 7

Innermost layer under choroid consisting of outer pigment cells, rods and cones, and axons of visual nerve fibres.

Question 8

What are the two fluid filled cavities separated by the lens?

Answer 8

1. Vitreous humor: gelatinous, between lens and retina
2. Aqueous humor: fluid, between cornea and lens

Question 9

What is the iris?

Answer 9

Contains circular and radial smooth muscle that control the amount of light entering the eye.

Question 10

What is the pupil?

Answer 10

Opening through which light enters the eye

Question 11

What is the lens?

Answer 11

Part of eye that bends light to focus it on the retina.

Question 12

What is the tapetum lucidum?

Answer 12

Additional reflective layer within the choroid that reflects light back towards retina. It improves sensitivity of vision under low light but causes blurriness in high light.

Question 13

Why do we change pupil size?

Answer 13

Control of light for optimization of light and dark conditions and providing a wide dynamic range.

Question 14

What is the relationship between depth of field and pupil size?

Answer 14

Small aperture (pupil size) = large depth of field

Large aperture (pupil size) = small depth of field

Question 15

What causes pupil size to change?

Answer 15

Parasympathetic stimulation contracts circular muscle, constricting pupil

Sympathetic stimulation contracts radial muscle, dilating pupil