Sec 3/Chap7/the sense organs Name Dissecting the eye of a mammal Goal



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Chapter 7, page 213


Sec 3/Chap7/the sense organs Name_________________


Dissecting the eye of a mammal


Goal

Locate and observe the structures of the eye.



Observation criteria

1. Identify the main structures of the eye.

____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________



2. In the table below, record the characteristics that will help you to identify each of these structures when observed during this lab.

Structure

Characteristics

Sclera (white of eye)





Choroid





Tapetum Lucidum (found in cattle and nocturn animals)





Retina





Cornea





Iris





Lens





Aqueous humor





Vitreous humor





Optic nerve





Pupil





Optic disk (blind spot)






Observations

Record your observations in the table below. Give the table a title.



Title: _____________________________________

Structure

Observations

Overall shape of eye




Structures attached around eye




Optic nerve

Colour:

Texture:



Iris

Colour:

Shape:



Liquid that fills eyeball

Name:

Colour:


Texture:

First membrane at rear of eye

Name:

Colour:


Thickness:

Texture:



Second membrane under the retina

Name:

Colour:


Thickness:

Third membrane at rear of eye

Name:

Colour:


Thickness:

Texture:



Fourth membrane at rear of eye

Name:

Colour:


Thickness:

Texture:



Membrane in front of iris

Name:

Shape:


Colour:

Liquid in front of iris

Name:

Colour:


Texture:

Lens

Colour:

Shape:


Texture:


Reflecting on your observations

1. Why is the pupil black in colour?










2. What is the function of the optic nerve?











3. What is the function of the muscles attached to the eye?











4. Are the two liquids collected from the eye similar? If not, how do they differ?











5. Why is the retina the first membrane at the back of the eye?








6. Which reflective membrane is present in a calf’s eye? (this membrane is not found in the human eye)








7. Did your observations help you to better understand the structures and functioning of the eye? Explain your answer.

















Materials

• gloves


calf eye

• scalpel

• dissecting forceps

dissecting scissors



• dissecting pan






Procedure

  1. Observe the exterior of the eye. Note the overall shape.

  2. use the scissor to cut away the fat and muscles.

  3. Locate the optic nerve. Note the colour and texture.

  4. Locate the cornea. Note the colour and shape.

  5. With the scalpel, make an incision on the edge of the cornea.

  6. Collect the liquid that seeps out the eye in dissection tray. Note
    the name, colour and texture of the liquid.

  7. Make an incision with the scalpel into the sclera. With the dissecting scissors, cut the eye into two parts by cutting along the incision.

  8. Front part of the eye: Use the scissors to cut away the cornea.

  9. Use the forceps to detach the iris

  10. Remove the lens. Try to use the lens as a magnifying glass.

  11. Empty out the gelatinous substance that fills the eyeball, in the dissecting tray.

  12. With the dissecting forceps, carefully detach the internal membrane at
    the back of the eye. Locate where this structure attached to.

  13. Spread out the membrane collected in the dissecting tray. Note the name, colour, thickness and texture.

  14. With the dissecting forceps, carefully detach the second internal
    membrane at the back of the eye. This membrane is called the tapetum Lucidum it is no present in the human eye but is found in the eyes of nocturne animal, cattle etc)

  15. Locate the optic nerve and make a longitudinal cut along the optic nerve all the way and to the sclera. Locate where the optic nerve is connected to eye.

  16. Finally tagged all the eyes parts with the provided tags. Call your teacher.

  17. Clean up and put away all materials as instructed.





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