How do we see?
-  About  80%  of the  information  that we receive from the environment is obtained through it. =>  The eye  is the  most...
-  We have  a pair of eyes. -  Each eye is  held and protected  in the  orbit  of the skull. orbit   skull
-   Each eye  is held by  eye muscles. -  Eye muscle  allows  the eyeball  to move  up and down, left and right  and in a ...
The eyes of  owls  cannot move  but their heads  can nearly rotate  360 o  .   Do you know ?
The part of eye we can see  is about  1/5 of  total surface area  of eyeball. Looking at the human eye 1   Label the drawi...
eyelid eyelash protective coat pupil iris Avoid  sweat  flowing into eyes Protect  eyes Avoid foreign objects ( insects ) ...
In bright light pupil becomes smaller side view =>   Avoid  strong light  to  damage eyes In dim light pupil becomes large...
Hole  allows light to pass through III  Internal structures of the eye 3   Label the drawing below. Thick  in middle , tra...
-   Ox eyes  and  human eyes  are similar  in structure . -  Dissecting  an ox eye  is a good way of studying the  structu...
-   Provides  attachment  for  eye muscles -   Maintains  the shape of  eyeball -   Protects  internal structure  of eyeba...
Functions  of main parts of the eye -acts as a protective layer  -outermost part of the eye -allows light to enter in the ...
-   Focuses  light  on the  retina Functions  of main parts of the eye lens
-   Focuses  light  on the  retina -  Maintains  the shape of  eyeball Functions  of main parts of the eye jelly-like fluid
Functions  of main parts of the eye iris under dim light under bright light
-   Changes  light  into  messages Functions  of main parts of the eye retina
-   Send  messages to the  brain Functions  of main parts of the eye optic nerve
In dim light,  pupils of  cats  and  owls  become  very large. For cats and owls, larger pupils  allow more light  to ente...
How  is an image formed  in the eye?  -  When we look at an object, =>  light   ray  is reflected from objects  into our e...
-  When  light  reaches   light-sensitive cells  on the retina , =>  messages  are sent to  the brain  by  optic nerve => ...
Showing the  image formed in an ox eye : -  Cut open  the  ox eye  and  stick  a piece of  semi-transparent paper  on the ...
Our eyes can see the   distant object  (flying bird up in the sky)  and the   near object   (a flower)  clearly . How can ...
-   Focusing images  on the  retina   is done by  lens. How do we  see things  at  different distances?  By  contraction  ...
-  Lens  becomes  thinner -  Focusing muscles  relax Near  object -  Focusing  muscles  contract -  Lens  becomes   thicke...
Why can we see  colours  ?
There are  two  types of  light-sensitive cells on the retina: rods cones
- Differences between  cones  and  rods : Cones Rods Number Condition Function Types Give   colour images Give  black  and...
- The brain   interprets  messages  from  cones  and forms  coloured images.
A bull  has  no cones  on its retina, therefore it  cannot  see any colour at all. Will  the bull  still run towards the c...
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Eye

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STRUCTURE OF HUMAN EYE AND

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Eye

  1. 1. How do we see?
  2. 2. - About 80% of the information that we receive from the environment is obtained through it. => The eye is the most important sense organ in our body. The eye
  3. 3. - We have a pair of eyes. - Each eye is held and protected in the orbit of the skull. orbit skull
  4. 4. - Each eye is held by eye muscles. - Eye muscle allows the eyeball to move up and down, left and right and in a circular way. eye muscle
  5. 5. The eyes of owls cannot move but their heads can nearly rotate 360 o . Do you know ?
  6. 6. The part of eye we can see is about 1/5 of total surface area of eyeball. Looking at the human eye 1 Label the drawing below. I Front part of the eye eyebrow eyelid protective coat eyelash pupil iris Activity Corner A
  7. 7. eyelid eyelash protective coat pupil iris Avoid sweat flowing into eyes Protect eyes Avoid foreign objects ( insects ) from entering eyes The eye is protected by the ______ , _______ and _______________. They prevent foreign objects from entering the eye. Light enters the eye through the _______ that is a hole at the centre of the ______ . eyebrow eyelid eyelash
  8. 8. In bright light pupil becomes smaller side view => Avoid strong light to damage eyes In dim light pupil becomes larger side view front view iris pupil front view
  9. 9. Hole allows light to pass through III Internal structures of the eye 3 Label the drawing below. Thick in middle , transparent and elastic ( thickness can be changed) A layer of white and elastic coat with the front part, cornea lens pupil protective coat Iris retina Have light-sensitive cells Connect with the brain optic nerve cornea jelly-like fluid
  10. 10. - Ox eyes and human eyes are similar in structure . - Dissecting an ox eye is a good way of studying the structures of our eyes.
  11. 11. - Provides attachment for eye muscles - Maintains the shape of eyeball - Protects internal structure of eyeball Functions of main parts of the eye Protective coat
  12. 12. Functions of main parts of the eye -acts as a protective layer -outermost part of the eye -allows light to enter in the eye cornea
  13. 13. - Focuses light on the retina Functions of main parts of the eye lens
  14. 14. - Focuses light on the retina - Maintains the shape of eyeball Functions of main parts of the eye jelly-like fluid
  15. 15. Functions of main parts of the eye iris under dim light under bright light
  16. 16. - Changes light into messages Functions of main parts of the eye retina
  17. 17. - Send messages to the brain Functions of main parts of the eye optic nerve
  18. 18. In dim light, pupils of cats and owls become very large. For cats and owls, larger pupils allow more light to enter the eyes, so they can move freely in dim light. Do you know ?
  19. 19. How is an image formed in the eye? - When we look at an object, => light ray is reflected from objects into our eyes. => The light passes through the cornea and lens and focuses on the retina to form an inverted image . inverted image
  20. 20. - When light reaches light-sensitive cells on the retina , => messages are sent to the brain by optic nerve => The brain interprets these messages as an upright image. How is vision produced ? => send messages
  21. 21. Showing the image formed in an ox eye : - Cut open the ox eye and stick a piece of semi-transparent paper on the back of retina. inverted image of candle
  22. 22. Our eyes can see the distant object (flying bird up in the sky) and the near object (a flower) clearly . How can the eyes focus on objects at different distances ?
  23. 23. - Focusing images on the retina is done by lens. How do we see things at different distances? By contraction or relaxation of the focusing muscles - thickness of lens can be changed. Focusing muscle
  24. 24. - Lens becomes thinner - Focusing muscles relax Near object - Focusing muscles contract - Lens becomes thicker Distant object
  25. 25. Why can we see colours ?
  26. 26. There are two types of light-sensitive cells on the retina: rods cones
  27. 27. - Differences between cones and rods : Cones Rods Number Condition Function Types Give colour images Give black and white images Work in bright light Work in dim light About 6 million About 1 . 2 billion One type (sensitive to red light, green light and blue light ) Three types
  28. 28. - The brain interprets messages from cones and forms coloured images.
  29. 29. A bull has no cones on its retina, therefore it cannot see any colour at all. Will the bull still run towards the cloth if the bullfighter uses a yellow one to replace the red one ? Do you know ?
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