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Structure and Function of the EyeSPE 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

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+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 retinao Motion, low light, no color

Cones -central retinao Highly centralized in the foveao Coloro 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