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Health 7
Chapter 14 Lesson 3
Healthy Eyes and Ears
I. THE STRUCTURE OF THE EYE
A.Your eyes enable you to distinguish shapes, colors,
movement and light.
B.The main parts of the eye are detailed below.
1.The cornea is a clear protective structure that
lets in light.
2.The iris is the colored part of the eye. It controls
the size of the pupil.
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3. The aqueous humor is the watery
fluid between the cornea and the lens. It
helps maintain pressure in the eye.
4. The lens is a clear, flexible structure
that focuses light on the retina.
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5. The retina is a thin layer of nerve
cells that absorb light. It covers the interior
back of the eye.
6. The optic nerve is a cord of nerve
fibers that carry messages from the retina to
the brain.
Healthy Eyes and Ears
Healthy Eyes and Ears
C. The human eye is similar to a camera
D. Light passes through the cornea,
aqueous humor, pupil and lens to the retina.
E. The nerve endings distinguish objects in
shades of black, white, and grey. Other
nerve endings called cones distinguish red,
blue and green.
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Healthy Eyes and Ears
F. A person who is missing one or more
kinds of cones in unable to distinguish
certain colors, an inherited condition called
color blindness.
http://www.bing.com/videos/search?q=how+
vision+works+video&FORM=VIRE1#view=d
etail&mid=D2AB65052EF6522A9837D2AB6
5052EF6522A9837
Healthy Eyes and Ears
II. PROTECTING YOUR EYES
A. Protecting your eyes from injury, dust and
overexposure to sunlight is a positive health
habit. Here are some guidelines:
a.wear protective eyewear when participating in an
activity that could injure the eyes
b.read, watch television and use the computer in a
well-lit room
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c. take breaks from using your eyes
d. avoid touching your eyeballs when
applying makeup
http://www.webmd.com/eye-health/goodeyesight
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III. GETTING YOUR EYES CHECKED
A. Two kinds of professionals provide eye
checkups:
a.An optometrist is a professional who checks your
vision and prescribers corrective lenses.
b.An ophthalmologist is a medical doctor who
specializes in the medical and surgical treatment of
the eyes, and who prescribers corrective lenses.
Healthy Eyes and Ears
B. If you wear glasses or contact lenses,
have your eyes checked once a year. If you
don’t wear glasses or contact lenses, every
two years is sufficient.
C. Common visions problems are:
a. Farsightedness - distant objects and clear,
but nearby objects appear blurred.
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2. Nearsightedness - A person can see
nearby objects clearly, but distant objects
appear blurred.
3. Astigmatism - Images are distorted or
blurred because of an irregularly shaped
lens or cornea.
http://www.webmd.com/eyehealth/understanding-vision-problems-
Healthy Eyes and Ears
E. Some vision problems can be corrected
with surgery.
1. Laser surgery to reshape the cornea
2.Surgery to remove cataracts
3.Transplants - lens, cornea
http://www.mayoclinic.org/testsprocedures/lasik-eye-surgery/multimedia/lasikeye-surgery/vid-20084660
Healthy Eyes and Ears
F. The examination of the eye consists of:
1. Inspection of the lens, cornea, pupil for
clearness
2.Check the eye for glaucoma - a disease of
vessels draining liquid in the eye. Early
detection can prevent blindness
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3. Check for cataracts - clouding of the
lens, corrected by surgery
4. Check vision - checks the size of
letters you can see from 20 feet away.
20/20 is considered good vision.
Healthy Eyes and Ears
IV. THE STRUCTURE OF THE EAR
A. You might think of your ears as external to
your head, but in fact they go deep into your
skull.
B.the ear has three main parts:
a.The outer ear - the fleshy curved part attached to
your head
Why do your think your outer ear is cup shaped
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2. The middle ear
3. The inner ear
Healthy Eyes and Ears
Healthy Eyes and Ears
V. HOW YOUR EARS WORK
A. Hearing involves a fairly complicated chain
of events.
a.First, the outer ear guides sound waves through the
auditory canal to the middle ear, where they cause
the eardrum to vibrate.
b.This vibration moves three tiny bones in the middle
ear; the hammer, anvil and stirrup.
Healthy Eyes and Ears
4. The bones then transmit the vibration
to the oval window in the inner ear.
5. The oval window causes fluid in the
cochlea to move.
6. The movement of this fluid sets tiny
hairs inside the cochlea in motion.
(15,000)
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7. The hair cells produce electrical
messages that travel through the
auditory nerve to the brain, which
interprets the messages enabling you to
identify the sound.
http://www.informedhealthonline.org/filmhow-does-the-ear-work.2402.en.html
Healthy Eyes and Ears
8. The Eustachian tube is the part of the
ear that allows air to pass from the nose to
the middle ear so the air pressure is equal
on both sides of the eardrum.
9. The Semicircular canals in the inner ear
control your balance.
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10. Two common balance problems are
dizziness and motion sickness.
E. Cochlear implants - can help hearing
impaired to hear
a.The device is a tiny microphone and sound
processor
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b. It picks up sound waves and converts
them to electronic signals
c. It passes the signals to a receiver
planted in the skin behind the ear.
Healthy Eyes and Ears
VI. PROTECTING YOUR EARS
A. Over time, loud noises can cause
permanent hearing loss.
B.A decibel is a measure of the loudness of a
sound.
http://www.bing.com/videos/search?q=what+is
+a+decibel&FORM=HDRSC3#view=detail&mid
=98C6268EDD98C302C28F98C6268EDD98C
Healthy Eyes and Ears
C. Tinnitus is a condition in which a
constant ringing sound is heard in the ear.
D. here are some ways to protect your ears.
1. Cover your ears with earmuffs, a hat and a
scarf in cold weather
2.Keep foreign objects and sharp objects and
cotton swabs out of your ears.
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http://www.healthyhearing.com/report/47773Swab-hearing-loss
3. Wear hearing protection, such as
ear plugs, when you are exposed to loud
noises at a concert, shooting,m or indoor
sporting event.
Healthy Eyes and Ears
http://listverse.com/2011/07/25/10-famousmusicians-with-hearing-damage/
http://www.hear-it.org/Farmers-risk-hearingloss