Chapter 9.4: The Senses

1. Chapter 9.4: The Senses

2. Vascular Tunics cont… • Pupil • Opening in iris • Color determined by: • Number of melanocytes • No melanocytes = blue eyes • Increasing number of melanocytes = green, brown and black eyes • Albinos = Pale gray or gray blue eyes

3. Figure 9.11

4. Vascular tunics cont… • Susensory Ligaments • Hold lens in place

5. Figure 9.10c

6. Neural Tunics • AKA: Retina • Innermost layer • Photoreceptors—cells that detect light • Rods—light sensitive • “low light vision” • Cones—color • Sharper images • Requires light

7. Figure 9.10c

8. Figure 9.12a

9. Retina cont… • Macula lutea • Where most cones are • In center—fovea centralis

10. Figure 9.12c

11. Retina cont… • Optic Disc • Origin of optic nerve • Contains blood vessels • No photoreceptors • “Blind spot” • Brain fills in missing information

12. Figure 9.12b

13. Chambers of the Eye • Anterior chamber—cornea to iris • Posterior chamber—iris to lens • Aqueous humor—fills both chambers • Maintains shape of eye • Transports wastes and nutrients • Vitreous body—in posterior chamber • Maintains shape of eye

14. Figure 9.14

15. Glaucoma • Interference with circulation • Increase in pressure • Leads to blindness if untreated

16. The Lens • Focus image on photoreceptors • Transparent • Contract and changes shape

17. Figure 9.14

18. Cataracts • Lens loses transparency • Due to drugs, injury or radiation • Most common: senile cataracts • Becomes cloudy with age • Visual clarity fades • Need bright lights to see • Treatment: • Remove old lens • Replace with artificial lens • Fine tune with glasses or contacts • No treatment = blindness