Eye Notes
Parts of sight sense Eyes Accessory organs Eyelids (palpebrae)-thinnest skin Protect eye Canthus-corners of the eye Eyelashes-hairs that prevent particles from getting into the eye Conjuctiva-membrane inside eyelids (prevent eyelids from sticking together) Conjunctivitis-pink eye Lacrimal apparatus-has a gland that produces tears/pink tissue in corner of eye Tears have lysozymes-antibacterial enzyme 6 muscles
Parts of outer eye Cornea-transparent window of the the eye Blindness-loss of transparency of cornea Can receive a donor cornea/no blood involved Parts of outer eye Cornea-transparent window of the the eye Focus entering light Covers colored portion of the eye Limited repair Sclera-white portion of eye Made of collagen and elastin Protect eye and attaches muscles Optic nerve Parts of fibrous tunic -Mechanical support and physical protection -Important for focus
Vascular Tunic (middle eye) Regulate amount of light entering the eye Control shape of lens (an essential part of the focusing process Choroid coat Vascular and nutritive Joined to sclera Melanocytes (pigments)-absorb excess light and keep inside eye dark (tons of pigments) Ciliary body-forms a ring around the eye Composed of muscles and ligaments Holds lens in position
Middle Eye (cont) Lens-behind the iris and pupil Held in place by suspensory ligaments Ciliary muscles and ligaments help to change its shape in order to focus Accomodation Relaxation creates flat shape to see distance Contraction creates convex shape to see close Cataracts-lens become cloudy and opaque Can cause blindness
Iris-part of middle eye Thin diaphragm of connective tissue and smooth muscle Colored portion of eye Thickness and # pigments determines eye color More is black, brown colors; less is blue and gray Adjusts the amount of light that enters the pupil The pupil is the opening at the center of the iris. Dark part of eye Aqueous humor-fluid between cornea and lens Provides nourishment and maintains shape
Smooth Muscle Role Regulates light by regulating pupil size Contract-small size so less light During bright light Relax-big size so more light During dim light
http://www.youtube.com/watch?v=0HzWmldLDHI&feature=related
Glaucoma Rate of aqueous humor formation is more than its rate of removal Builds pressure on the eye Blood vessels shut-rob cells of nutrients Cells die and may cause blindness
Inner Eye Parts Retina Contains a depression called fovea centralis Photoreceptors Thin and delicate Contains a depression called fovea centralis This produces the sharpest vision Optic Disc Where nerve fibers leave the eye and join the optic nerve Lacks receptor cells-known as blind spot Vitreous humor-liquid that fills the posterior cavity Floaters-when clumps form in this liquid
Light Refraction Refraction-bending of light waves Convex surface of cornea and the lens refracts light and converges the rays onto the retina Image is upside down and reverse Visual cortex interprets this image correctly
Visual Receptors Rods Cones Long and thin Provide black and white vision More sensitive to light Provide vision in dim light Cones Short and blunt Color vision Sharp image To see something in detail, a person moves the eyes so the image falls on the fovea centralis (has tons of cones) Cone numbers decrease as you move away from fovea centralis
Visual pigments Rhodopsin-light sensitive pigment Turns into opsin (protein) and retinal in the presence of light This break down triggers an enzyme to change the cell membrane of the rod cell Change causes a nerve impulse to be sent Nerve impulses travel away from the retina and are interpreted as vision. The light-sensitive pigments in cones are also proteins; there are three types, each containing a different visual pigment.
Visual Pigments (cont) The wavelength of light determines the color perceived from it; each of the three pigments is sensitive to different wavelengths of light. The color perceived depends upon which sets of cones the light stimulates: if all three sets are stimulated, the color is white; if none are stimulated, the color is black. Colorblindness-lack of cone pigments
Nearsightedness-myopia Farsightedness-hyperopia Concave lens Farsightedness-hyperopia Convex lens Ophthalmoscope-used to examine the interior of the eye