Structures of the Human Eye

Nota:

• Structure | Definition | Purpose | Where | Extra [Not in a table because it would be squished!]
• MISSING: [but all related to the retina. SO IT IS OKAY!]  - Fovea - Pigment Epithelium - Optic Nerve

1. Cornea
   1. The transparent "window" into the eyeball
      1. Therefore, most of the light rays are transmitted through

         Nota:

         • Remember definition of transmitted. [neither absorbed or reflects] 
      2. Transparent because
         1. Cornea contains no blood vessels or blood

            Nota:

            • [Blood or blood vessels would've absorbed light]
         2. Has an orderly arrangement of fibers
   2. Focuses and refracts light rays

      Nota:

      • Because it is curved To the retina
   3. Has transparent nerve endings [pain detectors]
      1. Purpose: forces the eye to close and produce tears if the cornea is scratched
   4. Continuous with the sclera
2. Sclera
   1. The tough outer layer of the eyeball

      Nota:

      • [covering the eye]
   2. Holds the structures in
   3. Forms a sheath around the optic nerve in the back

      Nota:

      • [it really does...look at diagram!] - pg 33
3. Aqueous Humor
   1. The watery fluid in the anterior chamber of the eye

      Nota:

      • Fluid is derived from blood -> has oxygen, nutrients -> and able to remove wastes
   2. Space between the cornea and the lens/iris
   3. Transmits and helps to focus the light rays
4. Crystalline Lens
   1. The lens inside the eye that enables the changing of focus

      Nota:

      • Lecture: adjustable refraction
      1. Ciliary muscle controls the shape of the lens
         1. Allows us to bring objects at different distances into focus
   2. Is transparent because there is no blood supply
5. Pupil
   1. Dark, circular opening at the centre of the iris in the eye, where light enters the eye
   2. Controls the amount of light that reaches the retina, via the pupillary light reflex
6. Iris
   1. The coloured part of the eye
   2. Expands and contracts the pupil
      1. Consists of a muscular diaphragm surrounding the pupil
         1. Regulates amount of light entering the eye by expanding and contracting the pupil
            1. Bright sunlight

               Nota:

               • Iris expands -> pupil shrink -> block most of the light that would enter the eye -> therefore image in the retina is not "overexposed"
            2. During low light

               Nota:

               • Iris contracts -> Pupils Enlarge -> Allows as much light as possible to enter the eye -> gives you the greatest change possible to see what there is to see.
7. Vitreous chamber

   Nota:

   • Space between the lens and the retina (posterior part of the eye)
8. Vitreous Humour
   1. The transparent fluid that fills the vireous chamber

      Nota:

      • Fluid: gel-like, viscous and transparent.  -> helps eye maintain its spherical shape -> refracts light rays -> Transparent: allows light rays to enter the retina
   2. Also contains small opaque (not transparent) particles

      Nota:

      • This can be seen as "floaters"
   3. Helps refract light
9. Retina

   Nota:

   • First, it goes from Focusing Light on the Retina -> Visual Problems
   • Then, lead into the retina information processing o.O - pg 38/ Still lecture 1 o.O
   1. A light sensitive membrane in the back of the eye

      Nota:

      • Receives an image from the lens
   2. Contains rods and cones
      1. Where light information is transduced into neural firing

         Nota:

         • - by the rods and cones - to the optic nerve [aka where transduction occurs]
         • Transduction: a change in energy source from one to another.  In this case light energy is changed into neural energy (that is the energy that the brain can interpret)

         Adjunto:

         • The Retina