1. Accessory Structures of the Eyes
Eyelids
Conjunctiva
Eyelashes
Eyebrows

2. Figure 17.5 Surface Anatomy of the Right Eye

3. Eyelids Superficial to deep Epidermis Dermis Subcutaneous tissue
Fibers of orbicularis oculi muscle
Tarsal plate
Connective tissue - support
Tarsal glands
Secrete fluid – prevent adhesion
Conjunctiva

4. Conjunctiva Thin protective mucous membrane
Nonkeratinized stratified squamous epithelium with goblet cells

5. Eyelashes Sebaceous ciliary glands – lubricating fluid Dry eyes =
Infection = Sty
Dry eyes =

6. Figure 17.6 Accessory Structures of the Eye

7. Lacrimal Apparatus Flow of Tears Lacrimal gland Lacrimal ducts
Lacrimal canals
Lacrimal sac
Nasolacrimal duct
Nasal cavity
Figure 17.6 Accessory Structures of the Eye

8. Extrinsic Eye Muscles Superior rectus Inferior rectus Medial rectus
Lateral rectus
Superior oblique
Inferior oblique
Figure 11.5 Extrinsic Eye Muscles

9. Extrinsic Eye Muscles Muscle Action on Eyeball Nerve Superior rectus
Elevation
CN III
Inferior rectus
Depression
Medial rectus
Adduction
Lateral rectus
Abduction
CN VI
Superior oblique
CN IV
Inferior oblique
Extrinsic Eye Muscles

10. Figure 11.5 Extrinsic Eye Muscles

11. Fibrous Tunic – Sclera and Cornea
Dense white fibrous coat
Gives shape to and protects eyeball
Posterior surface pierced by CN II
Cornea
Transparent fibrous coat
Nonvascular
Refracts light

12. Vascular Tunic Choroid Vascularized Melanocytes Absorbs light rays
Provides nutrients to retina

13. Vascular Tunic Ciliary body Ciliary processes secrete aqueous humor
Ciliary muscle
Alters shape of lens for near or far vision
Zonular Fibers

14. Vascular Tunic Iris (rainbow) Circular and radial smooth muscle fibers
Flattened donut
Regulates amount of light entering pupil

15. Pupil Little Person Heavily pigmented choroid and retina
Where light enters the eyeball
Pupil

16. Figure 17.8 Pupillary Response to Light Autonomic reflexes regulate pupil diameter in response to light levels.
oculomotor
neurons
Sphincter
Papillae

17. Retina (Nervous Tunic)
3rd, inner coat
Lines posterior eyeball
Beginning of visual pathway
Optic disk
Where CN II exits eye
Central retinal a. and v.
Bundled with optic nerve
Branch across retina

18. Macula Lutea and Fovea Macula “small flat spot” Lute “yellowish”
exact center of posterior portion of retina  visual axis of eye
Fovea  small depression in center of macula lutea

19. Figure 17.9 Blood Vessels in the Retina

20. Figure 17.7 Anatomy of the Eyeball

21. Retina Pigmented layer (nonvisual)
Aids choroid in absorbing stray light
Neural layer (visual)
Photoreceptor neurons
Bipolar neurons
Ganglion neurons

22. Figure 17.10 Microscopic Structure of the Retina

23. Figure 17.10 Microscopic Structure of the Retina

24. Figure 17.10 Microscopic Structure of the Retina

25. Photoreceptor Neurons
Rods
Black-and-white vision in dim light
Allow us to see shades of gray
Permit us to see shapes and movement
Cones
Specialized for color vision and sharpness of vision in bright light

26. Photoreceptor Neurons
Rods
Absent from fovea
Increase in density towards periphery
Cones
Most densely concentrated in central fovea

27. Lens Nonvascular Behind pupil and iris
Fine tunes focusing of light rays for clear vision

28. Interior of the Eyeball
Anterior cavity
Divisions
Anterior chamber
Posterior chamber
Filled with aqueous humor
Secreted by ciliary processes
Drained by scleral venous sinus
Posterior Cavity (vitreous chamber)
Filled with vitreous body

29. Figure 17.11 Anterior Cavity of the Eyeball

30. Aqueous humor filters out of capillaries
Ciliary processes of ciliary body
flows forward  posterior chamber
Pupil
anterior chamber
drains into scleral venous sinus (canal of Schlemm)  blood
Full replacement every 90 minutes

31. Recap Interior of eye divided into 2 cavities
Anterior Cavity  Aqueous Humour (FIG )
Anterior Chamber (behind cornea but in front of iris)
Posterior Chamber (behind iris and in front of lens)
Posterior Cavity  Vitreous body

32. Vitreous Body Located in the vitreous chamber (posterior chamber)
Between lens and retina
Vitreous body
Transparent gel
Holds retina flush against choroid
Even surface = clear images
Not constantly replaced
Phagocytic cells to clear debris

33. Disorders of the Vitreous Body
Flashes
Floaters

34. Image Formation Refraction Accommodation Pupillary restriction
Convergence

35. Refraction The bending of light rays
Cornea – 75%
Lens – 25%
Focused on retina
Images are upside down and reversed
Brain rearranges images
The lens fine tunes image focus and changes focus for near or distant objects
Parallel light rays ~20ft away

36. Accommodation Increase in curvature of lens
To focus on near objects (accommodation):
Ciliary muscle contracts
Pulls choroid towards lens
Releases tension on zonular fibers
Lens becomes more convex

37. Accommodation To focus on far objects: Ciliary muscle relaxes
Zonular fibers stretch in all directions
Lens flattens
Near point of vision

38. Accommodation

39. Constriction of the Pupil
Occurs simultaneously with accommodation
Prevents light rays from entering eye through periphery of lens
Results in a clearer image

40. Convergence
Eyeballs move medially so they are both directed toward an object being viewed

41. Photoreceptor Structure – rods and cones
OUTER SEGMENT
Rods - coins
Cones – pleat
INNER SEGMENT
Nucleus, Golgi, Mitochondria
PROXIMAL END
Coloured proteins that change shape when they absorb light.
Composed of:
Opsin (4 types)
Retinal
Types:
Rhodopsin in rods
3 others in cones
Fig pg. 590

42. Cis vs. Trans Structural Isomers Cis = “on this side”
Trans = “on the other side” or across

43. Photopigments Light bleaches photopigment
Cis-retinal is converted into trans-retinal
Trans-retinal separates from opsin
Forms a colourless product
Dark regenerates photopigment
Trans-retinal is converted into cis-retinal
Cis-retinal binds to opsin
Forms a coloured photopigment

44. Figure 17.15 Photopigment Bleaching and Regeneration
Cis-retinal fits into opsin, absorbs light photon, straightens to form trans- retinal = isomerization
chemicals form and disappear –receptor potential  
trans-retinal separates from opsin = bleaching  
Retinal isomerase converts trans-retinal to cis-retinal
Cis-retinal can bind to opsin again = regeneration

45. Photoreceptor Dark Activity

46. Photoreceptor Light Activity

47. Assigned Reading Read the Visual Pathway Pages 592-594
Make notes for yourself
Focus on understanding all of figure 17.17
COMPARE your notes to your lab partners. See what each of you focused on.
Go over eye lab again with models
Look at moveable eye model and place image on retina

48. The Visual Pathway Photoreceptors CN II Optic chiasm Optic tract
Thalamus
Optic radiations
Primary visual area

49. The Visual Pathway Chiasm = crossing point of optic nerves
At optic chiasm “nasal” axons cross over, but “temporal” axons remain ipsilateral

50. Figure 17.17 The Visual Pathway