1. SENSORY SYSTEM
STRUCTURE OF THE EYE

2. EYE
1” in diameter
Protected by orbital cavity, eyebrows, eyelashes, eyelids
Lacrimal glands
Tears empty into nasal cavity
Conjunctiva
Thin membrane lines eyelids
Wall of eye made up of three coats
Sclera
Choroid
Retina
Pages 189 and 190 figures 1 & 2

3. SCLERA Outer layer White of the eye
Tough coating, helps maintain shape of eye
Muscles responsible for moving eye attached to sclera:
Extrinsic muscles
See figure 10-3 and Table 10-1 pg 191

4. CORNEA Front center of sclera (clear part) no blood vessels
Transparent so light rays can pass through
Considered the “window” of the eye

5. CHOROID COAT Middle layer, contains blood vessels
Opening in front is pupil
Colored, muscular layer surrounding pupil is the iris
Intrinsic muscles
Change size of iris to control amount of light entering through pupil

6. LENS Crystalline structure located behind iris and pupil
Elastic, disc-shaped, biconvex
Job is to focus images on the retina
Situated between the anterior and posterior chambers
Anterior Chamber – filled with aqueous humor (watery fluid) and constantly replenished by blood vessels behind the iris
Posterior Chamber – filled with vitreous humor (transparent jelly-like substance)
Both help maintain the eyeball’s shape

7. RETINA Innermost layer Light rays focus image on retina
Image travels to the cerebral cortex via optic nerve
Rods
Sensitive to dim light
Cones
Sensitive to bright light and color
Optic disc
On retina, known as blind spot, nerve fibers that form optic nerve
See figures 10-5 and 10-6 pgs