Download Eye Dissection Notes

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
Happy Cow Eye Day!!
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 caused
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
“Astigmatism”
Curvature of the eye is
incorrect and causes
blurriness or distorted
vision
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.
“Myopia”
- “nearsightedness”
- Person has trouble
seeing things that are
far due to thick
cornea or lens or an
elongated eyeball
- Prescribed a concave
lens
“Hyperopia”
- “farsightedness”
- Person has trouble
seeing things that are
close due a short
eyeball, shallow cornea
or thin lens
- Prescribed a convex
lens
Middle Layer (cont.)
• 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
• Vitreous 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?
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 pigments which are
necessary for rod
sensitivity and seeing at
night.
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!