1. Eye Notes

2. Parts of sight sense Eyes Accessory organs
Eyelids (palpebrae)-thinnest skin
Protect eye
Canthus-corners of the eye
Eyelashes-hairs that prevent particles from getting into the eye
Conjuctiva-membrane inside eyelids (prevent eyelids from sticking together)
Conjunctivitis-pink eye
Lacrimal apparatus-has a gland that produces tears/pink tissue in corner of eye
Tears have lysozymes-antibacterial enzyme
6 muscles

4. Parts of outer eye Cornea-transparent window of the the eye
Blindness-loss of transparency of cornea
Can receive a donor cornea/no blood involved
Parts of outer eye
Cornea-transparent window of the the eye
Focus entering light
Covers colored portion of the eye
Limited repair
Sclera-white portion of eye
Made of collagen and elastin
Protect eye and attaches muscles
Optic nerve
Parts of fibrous tunic
-Mechanical support and
physical protection
-Important for focus

6. Vascular Tunic (middle eye)
Regulate amount of light entering the eye
Control shape of lens (an essential part of the focusing process
Choroid coat
Vascular and nutritive
Joined to sclera
Melanocytes (pigments)-absorb excess light and keep inside eye dark (tons of pigments)
Ciliary body-forms a ring around the eye
Composed of muscles and ligaments
Holds lens in position

7. Middle Eye (cont) Lens-behind the iris and pupil
Held in place by suspensory ligaments
Ciliary muscles and ligaments help to change its shape in order to focus
Accomodation
Relaxation creates flat shape to see distance
Contraction creates convex shape to see close
Cataracts-lens become cloudy and opaque
Can cause blindness

8. Iris-part of middle eye
Thin diaphragm of connective tissue and smooth muscle
Colored portion of eye
Thickness and # pigments determines eye color
More is black, brown colors; less is blue and gray
Adjusts the amount of light that enters the pupil
The pupil is the opening at the center of the iris.
Dark part of eye
Aqueous humor-fluid between cornea and lens
Provides nourishment and maintains shape

9. Smooth Muscle Role Regulates light by regulating pupil size
Contract-small size so less light
During bright light
Relax-big size so more light
During dim light

11. Glaucoma
Rate of aqueous humor formation is more than its rate of removal
Builds pressure on the eye
Blood vessels shut-rob cells of nutrients
Cells die and may cause blindness

12. Inner Eye Parts Retina Contains a depression called fovea centralis
Photoreceptors
Thin and delicate
Contains a depression called fovea centralis
This produces the sharpest vision
Optic Disc
Where nerve fibers leave the eye and join the optic nerve
Lacks receptor cells-known as blind spot
Vitreous humor-liquid that fills the posterior cavity
Floaters-when clumps form in this liquid

13. Light Refraction Refraction-bending of light waves
Convex surface of cornea and the lens refracts light and converges the rays onto the retina
Image is upside down and reverse
Visual cortex interprets this image correctly

14. Visual Receptors Rods Cones Long and thin
Provide black and white vision
More sensitive to light
Provide vision in dim light
Cones
Short and blunt
Color vision
Sharp image
To see something in detail, a person moves the eyes so the image falls on the fovea centralis (has tons of cones)
Cone numbers decrease as you move away from fovea centralis

17. Visual pigments Rhodopsin-light sensitive pigment
Turns into opsin (protein) and retinal in the presence of light
This break down triggers an enzyme to change the cell membrane of the rod cell
Change causes a nerve impulse to be sent
Nerve impulses travel away from the retina and are interpreted as vision.
The light-sensitive pigments in cones are also proteins; there are three types, each containing a different visual pigment.

18. Visual Pigments (cont)
The wavelength of light determines the color perceived from it; each of the three pigments is sensitive to different wavelengths of light.
The color perceived depends upon which sets of cones the light stimulates: if all three sets are stimulated, the color is white; if none are stimulated, the color is black.
Colorblindness-lack of cone pigments

19. Nearsightedness-myopia Farsightedness-hyperopia
Concave lens
Farsightedness-hyperopia
Convex lens
Ophthalmoscope-used to examine the interior of the eye