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Lacrimal apparatusConsists of lacrimal gland and several ducts

Ducts drain lacrimal secretions into nasal cavity

Gland continually release dilute salt solution (ie; tears) to anterior (front) surface through ducts

Tears (lacrimal secretion) flush across eyeball into

Lacrimal canals

Lacrimal sac

Nasolacrimal duct

Nasal cavity

Lysozyme enzymes destroy bacteriaCleans and protects eyeball

When there is an increase in lacrimal secretion, tears fill eyelids and nasal cavities causing congestion3 Tunics (Coats)1. OuterFibrousAqueous humor (fluid)2. Middlevascular

3. InnerSensoryVitreous humor (fluid)

Outer TunicSceleraWhite part of the eyeCornealight entersa lot of nerve endingsespecially painmost exposedcan be transplanted one individual to another without rejections because there is no blood flow, therefore, no connection to the immune system where rejections occur.Aqueous fluid between cornea and lens supplies nutrients and oxygen

Middle TunicChoroidPrevents light scatteringMerges in to ciliary bodies that the lens (used for focusing) attaches by ciliary zonule ligamentIrisColored part of the eyeRegulates amount of light entering eye to see clearlyPupildark = dialate light = constrictionInner Tunic (p.277 activity fig 8.5)

RetinaContains photoreceptors (rods & cones) that receive information by responding to lightHas vitreous humorGel-like fluid inside the eyeballHolds retina flat against choroid coat giving the eye its spherical shapeFovea centralis is the point on the retina where the light rays focusProduces the sharpest visionOptic disc is the place where the nerve fiber leave retina and become optic nervesCauses a blind spot because there are no photoreceptors here

Electrical impulse from the photoreceptors by:Bipolar cellsGanglion cellsLeaving retina via optic nerveWhen impulses are transmitted to optic cortexVision results

RODSMost dense at edge of retinaAllows us to see gray tonesPeripheral visionCONESMost dense in the center of retinaAllow us to see color

Blue + red = purpleAll 3 = whiteInterpretation of color happens in the brain NOT in the retina