A). Eyebrows: Protect from sunlight and stop perspiration from entering the eye.

B). Eyelids:

	Sweat and sebaceous glands (produce sandman=s sand)
	Muscles that open and close eye causing reflex blinking which protects and lubricates the eye.
	Eyelashes with nerve endings trigger blinking if anything touch

C). Conjunctiva

Lines interior of the eyelid and folds over the eye.

D). Lacrimal apparatus

Contains the lacrimal gland or tear ducts drain into the nasal cavity.

Lacrimal puncta: red dots on margin of each eyelid.

E). Extrinsic Eye Muscles

Eyeball is controlled by 6 strap-like muscles

II). Eyeball

A). Humors: fluids that fill internal cavity

B). Lens: Transparent biconvex, focusing apparatus of the eye & divides anterior & posterior segments.

C). Outer tunic: 

1). Sclera: Fibrous white dense connective tissue seen as white of the eye.

2). Cornea: Transparent fibrous connective tissue that allows light to enter. (bulges anteriorly)

D). Middle Tunic

1). Choroid:  dark supplies blood vessels and melanocytes that absorb light.

2). Ciliary body  tissue ring that surrounds the lens and controls the lens shape

3). Iris: Visible colored part; with pupil that allows the light to enter.

E).  Inner Tunic

1).  Retina (sensory area) Posterior interior layer extends to the cilliary body

Blind spot or optic disc where optic nerve passes through.

	ganglion cells
	bipolar cells
	photoreceptors.

 

A). Rods:

	Low light and peripheral vision receptors.
	Black and white vision.

B). Cones

Operate in bright light and provide color vision and visual acuity.

      Types of cones

	Pigment B (blue)
	Pigment G (green)
	Pigment R (red)

Various combinations of cones are stimulated by in-between colors

IV). Focus

A). For far-sight (seeing things far away) the lens is relaxed  

(It is preset to farsightness is caused by lose of elasticity).

B). For near-sight (seeing things near to by) the lens is bent.

	contraction of cilliary muscles
	constriction of pupil
	convergence of the eyeballs

V). Light and Vision and Perception

   A).  Properties of light

1). Light travels in waves and consists of small packets called photons.

2). Light reflects or bounces off of objects.

3). The objects absorb some wavelengths and reflects back others.

4). The color we perceive is the color that the object reflects.

B).  Real Image (upside down and backwards)

1). The reflected light enters the pupil and the lens at an angle

2). The real image is formed on the retina & it is upside down and reversed.

C). Receptors

1). Photoreceptors hyperpolarize.

2). Bipolar neurons feed into ganglion cells.

3). The stimulus passes down the optic nerve.

D).  Optic Chiasma

At the optic chiasma the nerves cross right to left & left to right but also continue on right to right and left to left.

So both optic tracts carry information from both eyes.

Partial crossing over means both tracts send a complete picture.

E).  Occipital Lobe

1). This signal reaches the thalamus.

(All cerebral cortex signals go through thalamus first)

2). Signals travels to the visual cortex in the occipital lobes.

3). Visual cortex sensory and association areas fuses the images resulting in depth perception or 3 dimensional vision so we perceive the entire field.

4).  Prefrontal Cortex makes a decision