Eye Eye Eye !• By the end of the dissection students will beable to identify various parts of the eye.
EYEThe eye is anextension ofthe brainIt helps us takein lightinformationfrom oursurroundings.This is how!
Eye brainproximity• Can you see :• the opticnerve bundle?• Spinal cord?
What are the parts of the eye?• Let’s use a diagram to help us get familiar withthe parts and pronounce them correctly!
CorneaCornea- transparent membrane that covers iris andpupil. Focuses light on the retina.
Pupil, Iris, ScleraPupil- hole passes different amounts of lightIris- colored part of the eye that controls the size ofthe pupilSclera- “whites” of the eye that forms outer covering
Aqueous Humor, Ciliary Muscle, LensAqueous Humor- nutritious fluid between the iris andthe cornea. As we age, it breaks down and we beginto see “floaters”Ciliary Muscles- produces aqueous humor andcontrols lens shapeLens- Bends light rays to the back of the eye –retina.Elastic so change in shape allows for focus onobjects close up or far away
Retina• Full of lightreceptorswhich aresensitiveto:• Cones-Colour• Rods- Lightlevels• Massivebloodsupply isalsoneededBlind Spot- site ofoptic nerveconnection
Vitreous Humor, Blind Spot, Optic Nerve,Vitreous Humor- transparent jelly-like fluid that fillsthe eye and refracts lightBlind Spot- area where opticnerve attaches. No retina islocated there so informationcannot be picked up; “Blind”Optic Nerve- sends messagespicked up by retina to the brain
Choroid Layer, Tapetum lucidumChoroid Layer- lies between thesclera and the retina it providesthe blood supply to the eye.Tapetum lucidum- iridescent filmunder the retina that providesanimals with “night vision”
Eye Dissection• Before we go over the dissection, let’s reviewthe parts of the eye and their function
• Select a place to make an incision of the sclera midwaybetween the cornea and optic nerve. Use the point of asurgical scissors to make a small cut through the sclera.Fluid should ooze out of the eyeball when you have cutdeeply enough.
• Arrange the two hemispheres of the eye as you see in thephotograph.• Observe the semi-fluid vitreous humor that fills the centralcavity of the eye. It is transparent in the living eye but mightbe cloudy in the preserved specimen
• The retina lines the the posterior cavity of the eye andextends forward to the ciliary body. Use your probe to liftand pull the retina back from the underlying choroid layer.• Notice that the retina is only firmly attached to the choroid atone place. This region is the optic disc or blind spot.
Remove the lens and place againstnewspaper to see that it is amagnifier!
• When the lens is removed, an opening, allowing light to enterthe eye is seen. This opening, the pupil is located in thecenter of the iris. Note the oblong shape of the sheep pupil,in humans the pupil is circular.• The back side of the iris can be seen just above the pointer inthe photograph.
Can you identify the parts? You willneed to to get credit during the lab
1. Cornea2. Sclera3. Optic Nerve4. Iris5. Pupil6. Ora Serrata (you do nothave to know thisstructure!)7. Ciliary Body8. Choroid9. Tapetum Lucidum10. Retina11. Lens12. Vitreous Humor
Clean up!• Follow clean up procedures:– Place all remains in a zip lock bag and place it in yourbox.– All dissecting instruments, tray and gel must bethoroughly washed in water.– Remove the paper towel from the tray and dispose ofit in the trash bag.– All used gloves are to be disposed of in the trash bag.– All goggles returned to the designated place.– Lab stations are clean and free of water/waste.– Each person washes their hands with soap and water.