2. صدق الله العظيم الاسراء اية 58

3. By Dr. Abdel Aziz M. Hussein Lecturer of Physiology Member of American Society of Physiology

4. The retina is the innermost photosensitive layer of the eyeball. It contains about 55 types of cells and 70% of total sensory receptors Histologically, it is formed of 10 layers Physiologically, 4 layers have special importance

8. Pigmented Epithelium Photoreceptors Bipolar cells Ganglion cells

10. Contains large amounts of melanin pigments

11. Produces a sticky ECF matrix

12. continual renewal of the outer segment of the rods and cones.

13. Breakdown and Resynthesis of the Photopigments

14. Stores Large Amount of Vit. A

16. Rods and Cones

17. Outer Segment

19. Outer segment Inner segment Inner Segment

20. Rod 120 millions Rod 120 millions Cones 7 millions Cones 7 millions Rod One pigment (rhodopsin) Rod One pigment (rhodopsin) Cone 3 pigments (iodopsin) Cone 3 pigments (iodopsin) Rods and Cones

22. Rods are peripheral cones are central

23. Rods and Cones Convergence

24. Rod more sensitive to lightLess accurate Cannot perceive colours Night vision Cone less sensitive to lightmore accurateCan perceive coloursDay vision Rods and Cones Functions

27. Bipolar cells Ganglion cells 1 st order neuron 2 nd order neuron Rods and Cones Convergence

30. Central retinal artery Choroidal blood vessels Supply pigmented epithelium and photoreceptors Supply inner layer of retina

31.  Retinal detachment (occurs between the pigmented epithelium and photoreceptors)  In this case the retina can resist degeneration for days due to its own blood supply (from central retinal artery) and diffusion of fluids across the detachment gap.  If the retina is not replaced rapidly within few days degeneration of the retina occurs.

34. Fundus oculi is the part of the retina which can be seen by ophthalmoscope. Fovea centralis Optic disc

35. Fovea centralis

37. 1. Decomposition of photosensitive pigment in rods & cones 2. Excitation of the photoreceptors by activated rhodopsin and generation of photoreceptor potential 3. Termination of excitation 4. Regeneration of photopigments

39. In DarkIn Dark

40. In LightIn Light

43. Within a sec the activated rhodopsin is inactivated by the enzyme rhodopsin kinase

46. THANKS