Do Now
• Research the following diseases and give a
sentence summarizing them
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Glaucoma
Conjunctivitis
“Floaters”
Corneal Abrasion
Astigmatism
Night vision blindness
10.9
Sense of Sight
Objectives
• To identify different visual accessory organs.
• To compare and contrast rods and cones.
• To explain various diseases of the eye.
Accessory Organs of the Eye
• Eyelids: contain skin, muscle, connective
tissue, and conjunctiva.
• Main Eye Muscles:
– Orbicularis Oculi: closes lid upon contraction.
– Levator Palpebrae Superioris: opens lid
Accessory Organs of the Eye
• Conjunctiva: mucous
membrane lining eyelids
and anterior surface of
eyeball (except the
cornea)
• Lacrimal Apparatus:
– Lacrimal gland- secretes
tears
– Superior and inferior
canaliculi- collect tears
– *Tears contain lysozyme
which acts as an
antibacterial agent.
“Conjunctivitis”
Inflammation of the
conjunctiva. Can be causes
by a viral infection or an
allergic reaction. Most
commonly caused by
bacteria which people call
“Pink Eye”
Accessory Organs of the Eye
• Extrinsic Eye Muscles:
– Superior Rectus
– Inferior Rectus
– Medial Rectus
– Lateral Rectus
– Superior Oblique
– Inferior Oblique
Accessory Organs of the Eye
• Extrinsic Eye Muscles:
Eye Structure
*The eye is about 2.5cm and is hollow
It contains 3 layers
1) An outer fibrous layer
2) A middle vascular layer
3) Inner nervous layer
Outer Layer
• Cornea:
– focuses entering light
rays
– Made of connective
tissue + epithelium
– Avascular
• Sclera: (the white part)
– Collagenous + elastic
fibers
– Protects eye
– Provides a place for
muscle attachment
Middle Layer
• Choroid coat:
– Provides blood vessels
– Contains melanocytes
• Ciliary Body:
– Aids in focusing
– Holds lens in place
• Lens:
– Changes shape to focus
– Flat=focus on distance
– Convex=focus on close
objects.
Middle Layer
• Iris:
– Colored part
– Contains muscles that
control pupil size
– Divides anterior/posterior
chambers
• Pupil:
– Opening in the iris
• Aqueous Humor:
– Watery fluid
– Secreted between cornea
and lens
– Provides nourishment
“Glaucoma”
Excessive production of
aqueous humor causes
pressure on the blood supply
from the optic nerve which
deprives cells of oxygen
causing them to die and the
patient to become blind.
Inner Layer
• Retina:
– Contains photoreceptors
• Optic Disc: (“Blind Spot”)
– Contains nerve fibers
– Contains central arteries
and veins
– Lacks receptors
• Viterous Body:
– Maintains shape
– Nourishes the posterior
cavity
“Floaters”
Bits of vitreous humor clump
and cast shadows on the
retina which causes
“floaters”. They can be seen
most commonly when
looking at the sky or a blank
wall. Do YOU have floaters?
Do Now
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What is the colored part of your eye called?
The white part?
What holds the lens in place?
Where are photoreceptors located?
What part of the eye does glaucoma effect?
Objectives
– Explain different diseases associated with the
eye.
– Identify different parts of a cow eyeball through
dissection.
– Perform various eye tests to observe different
functions and capabilities of the eye.
Light Refraction
• Light waves enter
your eye and your
lens focuses and
“bends” the light,
projecting the image
on your retina
Visual Receptors
• The eye contains
modified receptors in
the retina
– Rods: black and white
– Cones: color (3 types)
“Color Blindness”
The person usually lacks
one of the 3 types of cone
receptors causing them to
have trouble distinguishing
reds and greens.
“Night Blindness”
A deficiency in Vitamin A
reduces production of
retinal which is necessary
for rod sensitivity and
seeing at night.
“Astigmatism”
Curvature of the eye is
incorrect and causes
blurriness or distorted
vision
Lab- Cow Eye Dissection
– Gather all materials necessary for the
dissection.
– YOU MUST WEAR GOGGLES, AN APRON, AND
GLOVES!!!!
– Complete the dissection as instructed in the lab
handout and be sure to show me the pinned
structures for points!