Lacrimal apparatus Consists 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 bacteria Cleans and protects eyeball When there is an increase in lacrimal secretion, tears fill eyelids and nasal cavities causing congestion

3 Tunics (Coats) 1. Outer Fibrous Aqueous humor (fluid) 2. Middle vascular 3. Inner Sensory Vitreous humor (fluid)

Outer Tunic Scelera White part of the eye Cornea light enters a lot of nerve endings…especially pain most exposed can 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 Tunic Choroid Prevents light scattering Merges in to “ciliary bodies” that the lens (used for focusing) attaches by “ciliary zonule” ligament Iris Colored part of the eye Regulates amount of light entering eye to see clearly Pupil dark = dialate… light = constriction

Inner Tunic (p.277 activity fig 8.5) Retina Contains photoreceptors (rods & cones) that receive information by responding to light Has vitreous humor Gel-like fluid inside the eyeball Holds retina flat against choroid coat giving the eye it’s spherical shape Fovea centralis is the point on the retina where the light rays focus Produces the sharpest vision Optic disc is the place where the nerve fiber leave retina and become optic nerves Causes a blind spot because there are no photoreceptors here

1.Electrical impulse from the photoreceptors by: a.Bipolar cells b.Ganglion cells 2.Leaving retina via optic nerve 3.When impulses are transmitted to optic cortex 4.Vision results

RODS Most dense at edge of retina Allows us to see gray tones Peripheral vision CONES Most dense in the center of retina Allow us to see color Blue + red = purple All 3 = white Interpretation of color happens in the brain NOT in the retina