biology - eye

3. circular sheet of muscles, contains pigment that gives eyeball colour, controls amt of light entering
5. tough white coat, covers the eyeball, continuous with cornea, protects the eye from chemical damage
7. spot region where optic nerve leaves the eye, doesn't photoreceptors
10. protests cornea from mechanical damage
11. secretes mucus to keep front of eyeball moist
13. the process of the lens changing thickness to focus at objects at different distances
15. transparent circular and biconvex structure
17. black pigmented middle layer, prevents internal inflection of light, contains blood vessels
19. innermost layer of eye wall, contains photoreceptors , connected to nerve fibres

1. (body) contains muscles, controls thickness and curvature of lens
2. hole in the center of iris, allows light to enter eye
4. prevents excessive light from entering
6. red, green, blue, each time contains a different pigment, enables vairety of colours in bright light
7. spreads tears over the eyes for dust to be wiped off
8. (chamber)space behind the lens, keeps eyeball firm
9. stimulated even by dim light,
12. small yellow depression where images are focused, has cones but not rods
13. (chamber)space between lens and the cornea, keeps front of eyeball firm
14. gland secretes tears to wash away dust particles, keep cornea moist, lubricates conjunctiva
16. dome-shaped, transparent, refracts like rays into the eye
18. shields eyes from dust particles