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captures the light rays that are reflected off the object being looked at.


brings into focus the captured light rays before they hit the retina.


sees the captured light rays as an upside down image of the object being looked at.


located in the retina, they convert the upside down image into electrical impulses.

optic nerve

path these electrical impulses travel to reach the brain.


"turns the upside down image right side up and ""translates"" said image into ""information.""


outermost; tough, fibrous shell that forms the white of the eye.

choroids or uveal tract



innermost-highly vascular. The frontal portion of the choroid layer forms two separate structures: the outer ciliary body and the inner iris. Sheet of light-sensitive nerve cells that contain cones and rods. Each eye has appr. 100 million rods that respond to dim light for black-and-white vision and 7 million cones that perceive and respond to colors in daylight


anterior portion of the sclera. Convex and transparent structure. Allows the passage and refraction of light waves and consist of several layers, the innermost being the Descemet membrane, and the outermost being the Bowman membrane. There are no blood vessels within the sclera, but it does contain pain receptors.

ciliary body

muscular structure that is attached by suspensory ligaments to the lens supporting it. Changes shape to allow the lens to focus.


process of a body changing shape to allow the lens to focus


colored portion of the eye composed of smooth muscle fibers that regulate the diameter of the pupil (an opening in the center of the eye) to adjust for light


opening in the center of the eye


transparent elastic structure that refracts light waves and focuses them upon the retina.


found in the retina; each eye has over 100 million and they respond to dim light for black-and-white vision.


found in the retina, 7 million cones that perceive and respond to colors in daylight

aqueous humor

lymph-like fluid found in the anterior and posterior chambers of the eye and is secreted by the ciliary body and drains into the venous sinus.

vitreous chamber

cavity behind the lens

vitreous humor

jelly-like substance that fills the vitreous chamber


bone cavity that holds the eyeball; is lined with a layer of protective fat

accessory organs

protect the eye structures. Include eyebrows, eyelids, (also called palpebrae), eyelashes, and the ducts that produce tears.


shade the eyes from the sun and prevent perspiration or other objects from getting into the eyes. Also protects the eyeball from desiccation (drying up) by reflexively blinking appr. Every 7 seconds.

levator palpebrae muscle

raises the eyelid


thin mucous membrane that lines the interior surface of the eyelid and the exposed surface of the eyeball.

lacrimal duct

produce tears


constantly moisten and clean the exposed portion of the eyeball.

ocular muscles

control the movements of the eye and include 6 muscles that arise from the orbit and insert into the outer layer of the eyeball.

rectus muscles

4 muscles that maneuver the eyeball in the direction indicated by their names. (superior, inferior, lateral, and medial rectus muscles)

oblique muscles

2 muscles, the superior and inferior oblique muscles) rotate the eyeball on its axis.


cartilage loop that the superior oblique muscle passes through.

cranial nerves

innervate and control the muscles of the eye

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