The Eye
Extrinsic Eye Muscles Six skeletal muscles that move the eyeball Superior rectus- rotates eye up and medially Inferior rectus- rotates eye down and medially Medial rectus- rotates eye medially Lateral rectus- rotates eye laterally Superior oblique- rotates eye down and laterally Inferior oblique- rotates eye up and laterally
Eye Structure and Function 3 layers- outer fibrous tunic, middle vascular tunic, inner nervous tunic 1. Outer- Cornea- anterior portion transparent, light transmission, light refraction Sclera- posterior portion, opaque, protection Lens-Transparent, lies behind iris, largely composed of lens fibers, elastic, held in place by suspensory ligaments of ciliary body
2. Middle- Iris- anterior, pigmented, controls light intensity Ciliary body- anterior, pigmented, holds lens, moves lens for focusing Choroid coat- provides blood supply, pigments absorb extra light Anterior of eye filled with aqueous humor.
3. Inner- retina contains visual receptors continuous with optic nerve ends just behind margin of the ciliary body composed of several layers fovea centralis –produces sharpest vision optic disc – the raised disk on the retina at the point of entry of the optic nerve, lacking visual receptors and so creating a blind spot. vitreous humor – thick gel that holds retina flat against choroid coat
How We See Photoreceptors: Rods- produce colorless vision, produce outlines of objects Cones- provide vision in bright light, produce sharp images, produce color vision