Chapter 9.4: The Senses

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

Vascular Tunics cont…

Figure 9.11

Susensory Ligaments Hold lens in place

Vascular tunics cont…

Figure 9.10c

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

Neural Tunics

Figure 9.10c

Figure 9.12a

Macula lutea Where most cones are In center—fovea centralis

Retina cont…

Figure 9.12c

Optic Disc Origin of optic nerve Contains blood vessels No photoreceptors “Blind spot” Brain fills in missing information

Retina cont…

Figure 9.12b

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

Chambers of the Eye

Figure 9.14

Interference with circulation Increase in pressure Leads to blindness if untreated

Glaucoma

Focus image on photoreceptors Transparent Contract and changes shape

The Lens

Figure 9.14

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

Cataracts