The Special Senses

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Delicate two-layered membrane

Pigmented layer

Outer layer

Absorbs light and prevents its scattering

Stores vitamin A

Slide 24

Sensory Layer: Retina

Neural layer

Photoreceptor: transduce light energy

Cells that transmit and process signals: bipolar cells, ganglion cells, amacrine cells, and horizontal cells

Slide 25

Figure 15.6a

(a) Posterior aspect of the eyeball

Neural layer of retina

Pigmented

layer of

retina

Central artery

and vein of retina

Optic

nerve

Sclera

Choroid

Optic disc

Pathway of light

Slide 26

The Retina

Ganglion cell axons

Run along the inner surface of the retina

Leave the eye as the optic nerve

Optic disc (blind spot)

Site where the optic nerve leaves the eye

Lacks photoreceptors

Slide 27

Figure 15.6b

Pigmented

layer of retina

Pathway of light

Pathway of signal output

(b) Cells of the neural layer of the retina

Amacrine cell

Horizontal cell

• Rod

Photoreceptors

• Cone

Bipolar

cells

Ganglion

cells

Slide 28

Photoreceptors

Rods

More numerous at peripheral region of retina, away from the macula lutea

Operate in dim light

Provide indistinct, fuzzy, non color peripheral vision

Slide 29

Photoreceptors

Cones

Found in the macula lutea; concentrated in the fovea centralis

Operate in bright light

Provide high-acuity color vision

Slide 30

Blood Supply to the Retina

Two sources of blood supply

Choroid supplies the outer third (photoreceptors)

Central artery and vein of the retina supply the inner two-thirds

Slide 31

Figure 15.7

Macula

lutea

Central

artery

and vein

emerging

from the

optic disc

Optic disc

Retina

Slide 32

Internal Chambers and Fluids

The lens and ciliary zonule separate the anterior and posterior segments

Slide 33

Figure 15.4a

Central artery

and vein of

the retina

Optic disc

(blind spot)