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Biology LibreTexts

12.2: Organ Specimen

  • Page ID
    24200
  • Sheep Eye

    Wear gloves and goggles. Place a preserved sheep eye on a dissecting tray. You will also need scissors and a dissecting needle

    Outer Eye

    For each structure, indicate the tissue type

    Outer eye Structure Function Tissue type
    Optic nerve Sends impulses of vision to the brain.  
    Extrinsic eye muscles Move eyeball up and down, right to left  
    Fat

    On outside of the eye to provide cushioning

     
    Cornea

    Transparent covering over front of eyeball

     
    Sclera The “white” of eye. Fibrous membrane surrounding posterior 5/6ths of outer eyeball  

    Inner Eye

    Cut eyeball into anterior and posterior portions. Make the circular cut a few millimeters posterior to the edge of cornea. Once you have the eye in two pieces, observe the following structures. Relate each structure to its function in vision. Describe in your own words.

    • Vitreous humor - gel-like substance fills posterior portion of inner eyeball. Maintains inner eyeball shape.
    • Lens - clear, oval structure behind pupil.  The shape of the lens changes to focus light waves onto the retina for sharp vision.
    • Pupil - round opening that allows light to enter eye. The diameter of the pupil is controlled to let more, or less, light enter the eye.
    • Iris - responsible for eye color. Contains muscles that control the diameter of the pupil.
    • Retina - Cream-colored membrane stretched over inner back of the eyeball. Contains photoreceptors for vision. Composed of nervous tissue.
    • Choroid – Absorbs excess light

    * Discard eye in bucket, wash utensils and rinse the tray with water. Wash hands

    Label diagram of eye - Lateral view of human eyeball. Fill in A – H.

    12.2eyeDiagram.PNG
    http://commons.wikimedia.org/wiki/File:Eye_Diagram_without_text.gif

    Questions for Review

    Match the structure with the function

    12.2questions.PNG