1. Human Anatomy Senses

2. Conjunctiva

3. Covers the inner surface of the eyelids and the anterior surface of the eye. Membrane which produces mucous that lubricates the eye and prevents dryness. Protects the eye.

4. Fibrous Tunic

5. Sclera Functions: Protects eye Shapes eye Anchors eye muscles Cornea Functions: Transparent window for light entry Refracts light

6. Vascular Tunic

7. Choroid Functions: Provides nutrients to all eye tunics. Absorbs light preventing reflecting & scattering of light within the eye. Ciliary Body Functions: Ciliary processes secrete aqueous humor. Suspensory ligaments hold lens in place. Ciliary muscles pull on the ligaments to change the thickness of the lens. Iris Functions: Constricts or dilates to adjust the amount of light entering the eye.

8. Vascular Tunic Ciliary Processes Ciliary Muscles

10. Aqueous Humor Helps support the eye internally due to the intraocular pressure it produces inside the eye. Supplies nutrients & oxygen to the cornea, lens and portions of the retina. Carries away metabolic wastes from the cornea, lens and portions of the retina.

11. The pupil allows light to enter the posterior segment of the eye. The iris constricts or dilates to adjust size of the pupil.

13. Vitreous Humor Transmits light within the posterior segment. Supports the lens posteriorly. Holds the retina in place. Contributes to intraocular pressure.

14. Sensory Tunic

15. Retina Pigmented Layer Absorbs light Carries out phagocytosis Stores Vitamin A Neural Layer Contains photoreceptors (rods and cones) for visual perception Contains bipolar cells & ganglion cells for visual impulse transmission

16. Retina Fovea Centralis Contains only closely packed cones Provides acute color vision in bright light Macula Lutea Contains more widely spaced cones Other areas of Retina Contain only rods Provide night, dim light & peripheral vision Shades of grey only Optic Disc Contains no receptors Blind spot

17. Optic Disc Retina

18. Photoreceptors

19. Cones Are located in macula lutea but are most highly concentrated in the fovea centralis. Are sensitive to bright light (daylight) situations in which light is very intense. Each cone synapses with a single bipolar cell which synapses with a single ganglion cell. The axons of ganglion cells form the optic nerve to conduct visual images to the brain. Provide acute (sharp) color images (vision).

20. Cones

21. Photoreceptors

22. Rods Most highly concentrated in the retina outside the macula lutea Many rods synapse with a single bipolar cell Many bipolar cells may synapse with a single ganglion cell which carries stimuli to brain More sensitive & function only in dim light, night and peripheral vision Images are blurry and only in shades of gray

23. Visual Pigments Composed of two components Retinal - light absorbing molecule (made from Vitamin A) Opsin (four types made from protein) Opsin combined with retinal = visual pigment OPSIN + RETINAL = VisualPigment Depending on the type of opsin retinal is bound to, each of the four pigments will only absorb certain wavelengths of light.

24. Visual Pigments: RODS Retinal + Opsin = Rhodopsin (visual purple) Absorbs light throughout entire visible light spectrum (most sensitive to green) Functions only in dark, dim light & peripheral vision Light causes Retinal to change shape & separate from opsin causing nerve impulse Regenerate only in dark or dim light situations RHODOPSIN OPSIN RETINAL (Light) Impulse

25. Visual Pigments: Cones Retinal + Red, Green or Blue Opsin = Red, Green or Blue visual pigments Each Opsin absorbs light only in the area of the visible light spectrum it is sensitive to, ie, red cones, green cones & blue cones Function only in bright light (daylight) Provide sharp color images RedCone Red Opsin RETINAL (Light) Impulse GreenCone Green Opsin RETINAL Impulse

26. Lens Refracts (bends) light Focuses precise image on the retina (fovea) through accommodation (changing thickness)

27. Myopia (Nearsighted) Eyeball too long Distant objects focused in front of retina Image striking retina is blurred Correction: Concave lens or laser surgery to slightly flatten the cornea

28. Hyperopia (Farsighted) Eyeball too short, lens too thin or too stiff. Nearby objects are focused behind retina. Image striking the fovea is blurred. Correction: Convex lens

29. Astigmatism Irregular Curvature in parts of the cornea or lens Causes blurry image This may be corrected by specially ground lenses which compensate for the irregularity or laser surgery.

30. Cararact Clouding of lens due to aging, diabetes mellitus, heavy smoking, frequent exposure to intense sunlight or congenital factors Treatment: Lens Implant

31. Conjunctivitis Inflammation of the conjunctiva by: Bacteria, fungi or viruses Trauma

32. Glaucoma Most common cause of blindness. Increasing intraocular pressure compresses retina, optic nerve & blood vessels. Late symptoms include blurred vision & halos around bright objects Canal of Schlemn

33. Glaucoma

34. Color Blindness Congenital lack of one or more cone types Deficit or absence of red or green cones most common Sex-linked trait Most common in males What numbers can you see in each of these?

35. Night Blindness Impaired vision at night or in dim light situations Rhodopsin deficiency affecting rods Most common cause - prolonged Vitamin A deficiency Rods degenerate

36. Macular Degeneration Most common cause of vision loss after 65. Progressive deterioration of macula causing loss of central vision Dry Form - due to accumulation of pigments in macula due to reduced phagocytosis of cone debris by pigmented layer Wet Form - due to invasion of macula with new blood vessels from choroid causing scarring & retinal detachment

39. Middle Ear

41. Inner Ear Vestibule

42. Saccule Utricle

43. Maculae Monitors position of head in space Responds to straight-line changes in speed & direction Receptors for static equilibrium

44. Macula Receptor for Static Equilibrium

45. Inner Ear Semicircular Canals

47. Christa ampularis - receptor for dynamic equilibrium Responds to rotational (angular) movements Changes in rotatory velocity movements

48. Semicircular Canals Dynamic Equilibrium

49. Inner Ear Oval Window

50. Inner Ear Cochlea

51. Cochlea Unrolled Sprial Organ of Corti

52. Spiral Organ of Corti Receptor organ of hearing Different frequencies of vibrations (compression waves) in cochlea stimulate different areas of Organ of Corti Interpreted as differences in pitch

53. Inner Ear Round Window

54. Cochlea Oval Window Round Window

55. Acknowledgements Most of the figures used in this presentation came from the Benjamin Cummings Digital Library Version 2.0 for Human Anatomy & Physiology, Fifth Edition. Other figures came from public domain internet sources and software in the possession of the author.