1. The Human Eye Chapter 14

4. 14.2 The Human Eye Upper eyelid pupil cornea Lower eyelid iris Conjunctiva (covers sclera) Tear gland eyelashes

8. Chapter 14 The Human Eye Structure and Function of the Eye (Concept Map) January 11, 2010

9. Vertical Section of The Human Eye January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd.

10. Vertical Section of The Human Eye Attaches lens to ciliary body January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. suspensory ligament

11. Vertical Section of The Human Eye Controls amount of light entering the eye January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. iris suspensory ligament

12. Vertical Section of The Human Eye Refracts light rays; keeps eyeball firm January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. aqueous humour iris suspensory ligament

13. Vertical Section of The Human Eye Allows light to enter the eye January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. pupil aqueous humour iris suspensory ligament

14. Vertical Section of The Human Eye Refracts light rays into pupil January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. cornea pupil aqueous humour iris suspensory ligament

15. Vertical Section of The Human Eye lens Focuses light rays onto retina January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. cornea pupil aqueous humour iris suspensory ligament

16. Vertical Section of The Human Eye ciliary body Contains ciliary muscles which control curvature or thickness of the lens January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. lens cornea pupil aqueous humour iris suspensory ligament

17. Vertical Section of The Human Eye viterous humour Refracts light rays; keeps eyeball firm January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. ciliary body lens cornea pupil aqueous humour iris suspensory ligament

18. Vertical Section of The Human Eye Controls movement of eyeball January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. viterous humour ciliary body lens cornea pupil aqueous humour iris suspensory ligament rectus muscles

19. Vertical Section of The Human Eye Protects against mechanical injury January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. viterous humour ciliary body lens cornea pupil aqueous humour iris suspensory ligament sclera rectus muscles

20. Vertical Section of The Human Eye Pigmented black to prevent internal reflection of light; blood vessels bring oxygen and nutrients to the eyeball January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. viterous humour ciliary body lens cornea pupil aqueous humour iris suspensory ligament choroid sclera rectus muscles

21. Vertical Section of The Human Eye Region where images are sharply focused January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. viterous humour ciliary body lens cornea pupil aqueous humour iris suspensory ligament fovea (yellow spot) choroid sclera rectus muscles

22. Vertical Section of The Human Eye Transmit nerve impulses from eye to brain optic nerve January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. fovea (yellow spot) choroid sclera rectus muscles viterous humour ciliary body lens cornea pupil aqueous humour iris suspensory ligament

23. Vertical Section of The Human Eye Region over optic nerve; no photoreceptors, so insensitive to light blind spot January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. viterous humour ciliary body lens cornea pupil aqueous humour iris suspensory ligament optic nerve fovea (yellow spot) choroid sclera rectus muscles

24. Vertical Section of The Human Eye Light-sensitive layer containing cones responsible for colour vision in bright light and rods responsible for vision in dim light retina January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. viterous humour ciliary body lens cornea pupil aqueous humour iris suspensory ligament blind spot optic nerve fovea (yellow spot) choroid sclera rectus muscles

26. Chapter 14 The Human Eye Action of Iris in Bright Light January 11, 2010

27. Action of Iris in Bright Light January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Circular muscles of the iris contract 1

28. Action of Iris in Bright Light January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Radial muscles of the iris relax 2 Circular muscles of the iris contract 1

29. Action of Iris in Bright Light Pupil constricts and this reduces the amount of light entering the eye January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Radial muscles of the iris relax 2 Circular muscles of the iris contract 1 3

30. Chapter 14 The Human Eye Action of Iris in Dim Light January 11, 2010

31. Action of Iris in Dim Light January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Radial muscles of iris will contract Radial muscles of the iris contract 1

32. Action of Iris in Dim Light January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Radial muscles of the iris contract 1 Circular muscles of the iris relax 2

33. Action of Iris in Dim Light Pupil dilates and this increases the amount of light entering the eye January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Radial muscles of the iris contract 1 Circular muscles of the iris relax 2 3

40. Chapter 14 The Human Eye How Do We See? January 11, 2010

41. How Do We See? January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 1 Light rays are refracted through the cornea and the aqueous humour onto the lens object cornea lens aqueous humour

42. How Do We See? January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 1 2 The lens causes further refraction Light rays are refracted through the cornea and the aqueous humour onto the lens object cornea lens aqueous humour

43. How Do We See? January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 1 2 3 Rays converge to focus on retina The lens causes further refraction Light rays are refracted through the cornea and the aqueous humour onto the lens object cornea lens aqueous humour retina

44. How Do We See? January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 1 2 3 4 The image on the retina stimulates either the rods or the cones, depending on the intensity of the light Rays converge to focus on retina The lens causes further refraction Light rays are refracted through the cornea and the aqueous humour onto the lens object cornea lens aqueous humour retina image

47. Chapter 14 The Human Eye How Eyes Focus on Distant Objects January 11, 2010

48. How Eyes Focus on Distant Objects January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Parallel light rays from distant object enters eyes Vertical section of the eye 1

49. How Eyes Focus on Distant Objects January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Ciliary muscles relax Vertical section of the eye Enlarged portion of eye (front view) 1 2 2

50. How Eyes Focus on Distant Objects January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Suspensory ligaments become taut Vertical section of the eye Enlarged portion of eye (front view) 1 2 2 3 3

51. How Eyes Focus on Distant Objects January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Lens becomes thinner Vertical section of the eye Enlarged portion of eye (front view) 1 2 2 3 3 4 4

52. How Eyes Focus on Distant Objects January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Focal length increases Vertical section of the eye Enlarged portion of eye (front view) 1 2 2 3 3 4 5 4

53. How Eyes Focus on Distant Objects January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Vertical section of the eye Enlarged portion of eye (front view) Light rays from distant object focused on retina 1 2 2 3 3 4 5 6 4

54. How Eyes Focus on Distant Objects January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Vertical section of the eye Enlarged portion of eye (front view) Photoreceptors stimulated 7 1 2 2 3 3 4 5 6 4

55. How Eyes Focus on Distant Objects January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Vertical section of the eye Enlarged portion of eye (front view) Photoreceptors stimulated Nerve impulses produced by optic nerves 7 8 1 2 2 3 3 4 5 6 4

56. How Eyes Focus on Distant Objects Vertical section of the eye Enlarged portion of eye (front view) January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Photoreceptors stimulated Transmission of nerves to brain Nerve impulses produced by optic nerves 7 8 9 1 2 2 3 3 4 5 6 4

57. How Eyes Focus on Distant Objects Vertical section of the eye Enlarged portion of eye (front view) January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Photoreceptors stimulated Transmission of nerves to brain Brain interprets impulses Nerve impulses produced by optic nerves 7 8 9 10 1 2 2 3 3 4 5 6 4

58. How Eyes Focus on Distant Objects Photoreceptors stimulated Transmission of nerves to brain Vertical section of the eye Enlarged portion of eye (front view) Brain interprets impulses January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Person sees the distant object Nerve impulses produced by optic nerves 7 8 9 10 11 1 2 2 3 3 4 5 6 4

60. Chapter 14 The Human Eye How Eyes Focus on Near Objects January 11, 2010

61. How Eyes Focus on Near Objects January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Vertical section of the eye Diverging light rays from near object enters eyes 1

62. How Eyes Focus on Near Objects January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Vertical section of the eye Enlarged portion of eye (front view) Ciliary muscles contract 2 2 1

63. How Eyes Focus on Near Objects January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Vertical section of the eye Enlarged portion of eye (front view) Suspensory ligaments become slacken 3 2 2 3 1

64. How Eyes Focus on Near Objects Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Vertical section of the eye Enlarged portion of eye (front view) Lens becomes thicker January 11, 2010 3 2 2 3 4 1 4

65. How Eyes Focus on Near Objects Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Vertical section of the eye Enlarged portion of eye (front view) Focal length decreases January 11, 2010 3 2 2 3 4 5 1 4

66. How Eyes Focus on Near Objects January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Vertical section of the eye Enlarged portion of eye (front view) Light rays from near object focused on retina 3 2 2 3 4 5 6 1 4

67. How Eyes Focus on Near Objects January 11, 2010 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Vertical section of the eye Enlarged portion of eye (front view) Photoreceptors stimulated 3 2 2 3 4 5 6 1 7 4

68. How Eyes Focus on Near Objects Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Vertical section of the eye Enlarged portion of eye (front view) January 11, 2010 Photoreceptors stimulated Nerve impulses produced by optic nerves 3 2 2 3 4 5 6 1 7 8 4

69. How Eyes Focus on Near Objects Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Vertical section of the eye Enlarged portion of eye (front view) Photoreceptors stimulated Nerve impulses produced by optic nerves January 11, 2010 Transmission of nerves to brain 3 2 2 3 4 5 6 1 7 8 9 4

70. How Eyes Focus on Near Objects Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Vertical section of the eye Enlarged portion of eye (front view) Photoreceptors stimulated January 11, 2010 Nerve impulses produced by optic nerves Transmission of nerves to brain Brain interprets impulses 3 2 2 3 4 5 6 1 7 8 9 10 4

71. How Eyes Focus on Near Objects Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Vertical section of the eye Enlarged portion of eye (front view) Photoreceptors stimulated January 11, 2010 Nerve impulses produced by optic nerves Transmission of nerves to brain Brain interprets impulses Person sees the near object 3 2 2 3 4 6 1 5 7 8 9 10 11 4

73. Vertical Section of The Human Eye Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Pupil Reflex A reflex action in which the pupil changes size as a result of changes in light intensity.

74. Vertical Section of The Human Eye Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. Pupil Reflex In bright light