Download Structure and Function of the Eye

+
Structure and Function of the
Eye
SPE 516
+
The Bony Orbit
+
The Muscles of the Eye
(Extraocular muscles)
+
Superior and Inferior rectus

Superior rectus

Attached to the eye at 12 o’clock

Moves the eye up.
 Inferior rectus

Attached to the eye at 6 o’clock

Moves the eye down.
+
Lateral Rectus

Lateral Rectus

Also called the external rectus

Attaches on the temporal side of the eye

Moves the eye toward the outside of the head (toward the temple)
+
Medial Rectus

Medial Rectus

Also called the internal rectus

Attached on the nasal side of the eye

Moves the eye toward the middle of the head (toward the nose)
+
Superior Oblique

Attached high on the temporal side of the eye.

Passes under the Superior Rectus.

Moves the eye in a diagonal pattern -- down and in.

Travels through the trochlea
+
Inferior Oblique

Attached low on the nasal side of the eye.

Passes over the Inferior Rectus.

Moves the eye in a diagonal pattern -- up and out.
+
The Nerves That Control the
Muscles of the Eye

Third Cranial Nerves

Fourth Cranial Nerves

Sixth Cranial Nerves
+
Lids and Lashes

Main function is the protection of the eye.

They also help to distribute tears which wash and lubricate the eyes.
+
The Lacrimal System -- Tears
+
The Refractive Structures

These structures bend the light so that a clear image is produced.

They are:

tears

conjunctiva

cornea

aqueous humor

lens

vitreous humor
+
Chambers of the Eye
1. Anterior chamber – from cornea to iris
2. Posterior chamber – from iris to zonules and lens –
These two are responsible for the production and drainage of the aqueous
which is produced continuously throughout your life.
Aqueous is produced in the posterior chamber by the ciliary body travel
through the iris to drain out the anterior chamber (through the Canal of
Schlemn)
3. Vitreous – gel like –gives the eye its shape not produced – damage or
loss can cause retinas to fall or tear
+
+
Layers of the eye

Sclera and Cornea

uveal tract


Choroid

Iris

Ciliary body
retina
+
Sclera and Cornea

Form the outer layer of the eye – 1/6 cornea and 5/6 sclera

Cornea is clear- sclera is white (they transition at the limbus)

Very tough and provide protection

Sclera maintains shape of the eye

Cornea is the major refractor of the eye
+
Uveal Tract

Choroid – vascular layer, major supplier of nutrients and blood
supply to the eye

Iris – Controls light that enters eye

Cilliary body- produces aqueous humor to bathe lens and provide
nutrients to lens and cornea and provides accommodation.
+
The Retina
The retina is made up of cones and rods

Rods -peripheral retina
o

Motion, low light, no color
Cones -central retina
o
Highly centralized in the fovea
o
Color
o
Fine detail
+
The Optic Pathway

Begins at the optic nerve.

Impulses cross and partially split at the optic chiasm.

After the chiasm, it becomes the optic tract.

Lateral geniculate bodies (sensory way stations)

Some fibers go to the colliculus (located in the mid brain)
+
Optic Pathway (cont.)

The other fibers fan out into the visual cortex which is located at the
top and back of the brain.
+
Vision and the Brain


Primary visual cortex (Striated Cortex) -
spatial organization of a scene

shapes of objects

brightness and shading of parts of objects
Secondary visual cortex (Prestriated Cortex) -
pattern recognition
+
The Brain and Vision (cont)


Temporal Lobes

center for visual learning

recognition by sight
Midbrain -- Limbic sector


emotional responses to visual stimuli
Midbrain -- Superior Colliculus -
guides visual attention