Eye - Structure: 3 Tunics (=Layers)

Iris

Anterior "Colored donut of muscle" (Intrinsic muscle) opening = pupil Sphincter pupillae Dilator pupillae Refulates amount of light intering the eye

Cornea

Anterior 1/6 of eye Transparent

Lens

Biconvex Transparent Flexible Changes shape to allow for the focusing of light on the retina

Rods

Black and white vision, respond to low intensity light (night)

Cones

Color vision Respond to high intensity light (daylight)

Internal (Sensory) Tunic

Composed of the retina Pigmented layer Neural layer

Ciliary Processes

Contain capillaries that secrete aqueous humor Part of ciliary body

Neural Layer

Inner layer Composed of photoreceptors Rods Cones

Macula Lutea

Lateral to blind spot Oval region Contain Fovea centralis

Fovea Centralis

Minute pit in center of macula lutea Contains only cones Where critical "detailed" viewing takes place

Pigmented Layer

Outer layers of internal tunic No photoreceptors Stores vitamin A

Fibrous Tunic

Outermost, avascular Sclera Cornea

Ciliary Body

Part of vascular tunic Ciliary (an intrinsic muscle) which is attached to the lens by Suspensory ligaments. Muscles changes shape of lens (=focus)

Choroid

Posterior 2/3 of eye Vascular and pigmented Nourishes retina and sclera by diffusion

Sclera

Posterior 5/6 of eye Nontransparent The "white" of the eye

Sphincter Pupillae

Pupillary constrictor Contricts pupil

Dilator Pupillae

Pupillary dilator Dilates pupil

Vascular Tunic

Uvea Middle Layer Choroid Ciliary Body Iris

Blind Spot

Where the optic nerve exits the eye Optic Disk No rods of cones