(Note: Show a video of a woman crossing the EDSA during a rush hour. Show smoke belching bus, honking cars, the heat of the sun, etc. Show her covering her lower face from the elements

1
What Is This Module About?
We learn from the things around us. We learn from what we see, hear, feel, taste
and smell. We recognize objects, sounds, smells, tastes, pleasure, pain, pressure and
temperature through our sense organs — the eyes, nose, ears, skin and tongue.
Have you ever wondered how your sense organs work? What do you think would
happen to your life if you lose even one of them? Would you still be able to do the
things that you usually do?
This module will illustrate how important our sense organs are to our daily lives.
It will discuss how they work and the diseases that may affect them.
The module is divided into three lessons:

(Show videos of the following:

Lesson 1 – The Organs of Sight and Hearing
Lesson 2 – The Organs of Smell, Taste and Touch
Lesson 3 – Sensory Diseases and Their Prevention


What Will You Learn From This Module? (Voice
After studying this module, you should be able to:
♦ identify the various sense organs and their corresponding senses;
♦ describe the structure and function of the sense organs and their importance;
and
♦ cite different diseases and ailments related to the sense organs and their
respective symptoms.
2
Let’s See What You Already Know


Before you start studying this module, take this test first to find out what you
already know about the topic.
A. Multiple Choice. Encircle the letter of the correct answer.
1. Our eye is our organ for our sense of _.
a. smell c. vision
b. hearing d. touch
2. The thin layer of tissue that lines your eyelids and nasal cavity is called
the
_.
a. lining c. skin
b. mucous membrane d. dermis
3. The innermost layer of cell inside your eye is called the
_.
a. mucous membrane c. retina
b. conjunctiva d. choroid
4. The visible part of your ear is called the .
a. ear c. flaps
b. auricle d. shell
5. You hear sounds through
.
a. vibration c. noise
b. music d. light
6. The smallest bones of your body are found in your
_.
a. eyes c. mouth
b. nose d. ears
7. Olfaction pertains to your sense of _.
a. smell c. sight
b. touch d. taste
8. Your _ are groups of cells inside your mouth that
detect the taste of the food you eat.
a. tongue c. taste buds
b. teeth d. saliva
3
9. The biggest sense organ of your body is your
_.
a. nose c. skin
b. lips d. eyes
10. Your sense of touch is also called your sense.
a. olfaction c. balance
b. vision d. tactile
B. Write the sense organs affected by the following disorders or diseases.
Write eye, ear, nose, tongue or skin in the space provided before each
number.
_ 1. Carbuncle
_ 2. Otitis media
_ 3. Rhinitis
_ 4. Sty
_ 5. Aguesia
Well, how was it? Do you think you fared well? Compare your answers with
those in the Answer Key on page 51.
If all your answers are correct, very good! This shows that you already know
much about the topic. You may still study the module to review what you already
know. Who knows, you might learn new things as well.
If you got a low score, don’t feel bad. This only shows that this module is for
you. It will help you understand important concepts that you can apply in your daily
life. If you study this module carefully, you will learn the answers to all the items in
the test and a lot more! Are you ready?
You may go now to the next page to begin Lesson 1.
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LESSON 1
The Organs of Sight and Hearing
Have you ever wondered what will happen to you if you lost your eyes and ears?
How will you ever see the beauty of life and hear the sound of music?
We learn through our senses… we learn from what we feel, taste and smell. More
importantly, we learn from what we see and hear. These two are the most developed
among our senses. We can easily identify our surroundings through the use of our
eyes and ears.
You will learn more about your eyes and ears as you study this lesson. This
lesson will discuss the functions and structures of your eyes and ears.
After you finish studying this lesson, you should be able to:
♦ explain how the eyes and ears function;
♦ identify the parts of your eyes and ears; and
♦ explain the functions of each part of your eyes and ears.
Let’s Think About This
Go outside and take a short walk. Observe your surroundings. Where are you
now? What do you see? What do you hear?

_
What if you can’t see — will you still be able to know what is around you? How?
_
_
Even if you can’t see you can learn what is happening through the sounds that you
hear. But what if it’s the other way? What if you can see what is happening around you
but you can’t hear a sound from your surroundings? Do you think you will be able to
understand what is happening around you? Explain your answer.
_
_
If you answered yes, that’s correct. You can still understand your surroundings by
looking at them. However, it will be more difficult if you can’t hear a sound. For
example, someone is telling you something, it is difficult to understand him or her if
you can’t hear what he or she is saying.
5
We find out about the world we live in through our senses. We learn through our
senses. We see with our eyes, and our sense of sight tells us about things that are
outside our bodies. Our eyes give us pictures or images of the way things look. They
show us light, color, shape and size. The eyes and ears receive messages from the
outside world and transmit them to the brain. Our eye is our organ for vision. Our ear,
on the other hand, is our organ for hearing.
Let’s Study and Analyze
How do your eyes see?
Your eye has many parts and each one of them helps you see.
Try blinking one of your eyes in front of a mirror. Can you see the skin that
covers your eye every time it closes? This is called the eyelid. It protects your eye
from tiny objects that might enter it. Below your eyelid is a thin layer of tissue called
the mucous membrane. It is always wet because there are tear glands that produce
tears on top of your eye behind the eyelids. The tears help clean your eye every time
you close your eyelid. The short hairs on the tip of your eyelid are called eyelashes.
They brush away tiny objects and dirt from entering your eye.
There are three cell layers or linings inside your eyeball. They are the:
a. Sclera. This is the white part of your eye. In front of it, on top of the
colored part of your eye (iris), is a transparent covering called the cornea.
The cornea protects the lens of your eye. It also allows light rays to enter the
eye and helps to focus them. A thin layer of transparent tissue covers the
sclera. This tissue is known as conjunctiva.
b. Choroid. This is the middle layer of the wall of your eyeball. It absorbs
excessive light and gives rise to the iris, which surrounds an opening called
the pupil.
c. Retina. This is the innermost layer of your eye where light-sensitive cells
are found.
Outer Parts of the Eye Inner Parts of the Eye
tear gland
eyelid
eyelashes
sclera
choroid
cornea
lens eyebrow
iris
pupil
pupil
retina
blind spot
optic nerve
6
Let’s Try This
To learn more about how your eye and its parts function, do the activity below.
Stand near a mirror in a dimly-lit room
just below a source of light. Observe the
movement of your eyes.
What happened to the black dot in the
middle of your eye? Did it widen (dilate)?
Or did it narrow (contract)?
_

_
Ask someone to turn on the light.
Observe the movement of one of your
eyes.
What happened to the black dot in
the middle of your eye? Did it widen
(dilate)? Or did it narrow (contract)?

_
_
What do you think is the reason for this movement?

_
_
The activity tells you how the pupil works. To learn the answers to the questions,
study the illustrations below.
Your eye is like a camera. It reacts to light. Can you see the black dot in the
middle of the colored part of your eye? That is called the pupil.
Dim Light
Opening of
camera widens
Pupil widens
Camera na
pupil pupil
7
Let’s Learn
The pupil is like the opening of a camera. In dim light, the opening widens. In
bright light, it narrows. The pupil controls the amount of light that enters the eye. If it
is too bright, the pupil narrows to protect the eyes from too much light. If it is dim,
the pupil widens so that more light can enter into the eyes.
The eye receives light rays that are reflected from
an object. The light goes in through the pupil.
The colored part that surrounds the pupil is called
the iris. Its color comes from a substance called
melanin. Melanin absorbs strong light that might shock
the eye. Strong light could cause blurred vision.
Let’s Review
Why does a welder in a welding shop use dark protective eyewear or a welding
mask while working?
_


Compare your answer with that in the Answer Key on page 51.
Let’s Study and Analyze
You have just learned how the pupil works. Consider that stage (when light enters
the pupil) as just a door or an entrance. A lot of things still happen after the light
enters the door and the door closes.
As the light enters the eye, it passes through the lens.
Refer to the illustration on page 5. Were you able to find the lens of the eye? If
so, let’s continue.
The lens helps at focusing the
image to make it clearer. As the light
goes through the lens, it turns the light
upside down. The lens focuses the light
rays or the inverted image on the back of
your eye or on the retina.
iris
pupil
The Eye
i
m
a
g
e
retina
light
lens
8
As stated earlier, the retina is the innermost layer of the wall of the eyeball.
Light-sensitive cells absorb light rays (inverted image), changing them into electrical
signals.
There are two types of light-sensitive cells inside the retina, the rods and the
cones. Do you know what they are for?

_

a. Rods. There are 120 million rods inside your retina. These enable the eyes
to see different shades of gray and to see in the dark. They detect black and
white.
b. Cones. There are 6 million cones inside your retina. These enable the eyes
to see colors and sharp images in bright light. They detect color.
These cells turn the inverted image into electrical signals that travel along the
optic nerve to the brain. It is important to note that there are NO rods and cones at
the area where the optic nerve enters your eye. This is the blind spot (refer to the
illustration on page 5) of your eye. The optic nerve carries the message to your brain.
The brain then decodes the electrical signals, seeing the object the right side up.
Let’s Review
Give the functions of the following parts of your eye:
Structures in the Eye Func
1. Sclera
2. Cornea
3. Choroid
optic
nerve
Cells in the retina can sense light.
cones
inside portion of the retina
rods
sclera
choroid
9
Compare your answers with those in the Answer Key on page 51.
Let’s Study and Analyze
How does our ear work?
Our ear, just like our eye, has many parts that make us hear.
Read the discussion below on the parts of the ear to familiarize yourself with the
different ear functions.
The ear is divided into three regions: the outer ear, the middle ear and the inner ear.
The outer ear is the visible part of the ear. It is composed
of the auricle and the external auditory canal.
Try touching the curved flaps beside your head, which you
call your ‘ear.’ That part is called the auricle. The auricle, or
outer portion of your ear, is the one that collects sounds from
your surroundings.
Structures in the Eye F
4. Pupil
5. Iris
6. Retina
7. Lens
8. Optic nerve
eustachian
tube
semicircular canals
ANATOMY OF THE EAR
auricle
eardrum
external
auditory canal
auditory
ossicles
cochlea
auditory
nerve
inner ear
middle ear
outer ear
10
Why are your ears shaped like seashells?


_
Ears are shaped like seashells because that’s
the best way it can collect sounds from your
surroundings. Isn’t it that when somebody is
whispering to you, you place your hand beside
your ear like the child in the picture? Why do you
do so?


Placing your hand beside your ear makes you hear more clearly what your friend
is saying, right? This happens because your hand helps your ear pick up the sounds
coming from your friend.
Get a mirror and place it beside your head. Can you see a canal or a tube? It is
where the sound passes. It is called the external auditory canal. It is the opening of
the ear. That tube goes inside your ear until it reaches the eardrum.
The eardrum is a very thin membrane or tissue. It is only .004 of an inch (0.1
mm) thick, stretched along the opening of the external auditory canal. Sounds that
pass through the external auditory canal strike the eardrum, causing it to vibrate. Can
you find the eardrum in the illustration on page 9? After you locate the eardrum,
continue with the activity below.
Let’s Try This
Inside your ear is a drum that produces vibrations, which the brain would interpret
as sounds. To learn about how your eardrum works, do the activity below.
Get the following materials:
♦ a big can of milk
♦ strings or rubber bands
♦ a piece of cloth enough to cover the top
of the can
♦ a pair of scissor
♦ a can opener
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Procedure:
Step 1. Open both ends of the can Step 2. Get the piece of cloth
using the can opener. and cover one end of the
can.
Step 3. Secure the cover by tying the cloth tightly.
Have you followed the procedure correctly? What do you have now? A drum!
Now, try tapping the top of the drum slowly.
Can you hear sounds? _ Yes _ No
Can you feel the vibrations? _ Yes _ No
If you can’t feel anything, try covering your drum more tightly. Now tap your
drum again. Can you feel the vibrations? Try tapping harder. As the sounds become
louder, the vibrations become stronger, right? Try tapping it harder than the second
time. Will you agree that if you tapped it too hard, your drum might break? Yes
No
What if you listen to a very loud sound or music, will your eardrum break too?
Why do you say so?
_
_
_
If you answered yes, you are correct! What happens inside your ear is almost the
same as what happens to the drum when it is tapped. You hear sounds through
vibrations. You can hear the music or the voice coming from the radio because it is
vibrating — it causes vibrations in the air. If the sounds you hear are too loud, your
eardrums also vibrate strongly. If this happens, the eardrums might get damaged.
3
1 2
12
Let’s Think About This
How do you take care of your ears?
_


Do you think it is important to keep them clean all the time? Why?
_
_
_
Have you finished answering the questions? If you take care of your ears by
always keeping them clean, that’s very good! If your auricles are dirty, dirt and
bacteria could enter into the inner portion of your ear. Those might cause ear
infections that can lead to diminished hearing or a total loss of hearing. You will learn
more about ear disorders in Lesson 3.
You can keep your ear clean by using cotton buds. Put some oil on the tip of the
cotton bud and gently clean your auricles. You can also insert it a little bit into your
external auditory canals to clean them. Be careful not to insert the cotton bud too
deep. You might damage your eardrum. Do not use sharp objects when cleaning your
ears. You might damage the skin and the lines of the external auditory canal.
Let’s Study and Analyze
You learned that your auricle collects sounds that pass through your external
auditory canal. As they travel in the ear canal, they strike the eardrum and make it
vibrate. These vibrations make the other parts of the ear, called the middle ear,
vibrate too.
A very small cavity or pocket in the skull bone, located inside the eardrum, forms
the middle ear. Inside this small pocket is a chain of three small bones, called the
auditory ossicles. This chain of small bones stretches from the eardrum to the oval
window. The oval window is the entrance to the inner ear, which you will learn about
later.
Do you know that the three small bones found in your middle ear are the smallest
bones of your body?
The three bones occur in the following order:
hammer (malleus) – This bone is the largest auditory ossicle. It connects
the eardrum to the anvil. It is attached to the tympanum.
13
anvil (incus) – This bone is located between the hammer and the stirrup.
stirrup (stapes) – This bone is attached to a thin sheath of tissue or a
membrane called the oval window.
Let’s Think About This
What do you think happens when the eardrum vibrates?

_
_
If you answered that the chain of bones in the middle ear vibrates too, you are
correct!
When the sound vibrations that pass through the external auditory canal hit the
eardrum, the eardrum vibrates. The vibrations that are produced in the eardrum also
cause the tympanic membrane of the tympanum to vibrate. Since the hammer lies
between the tympanum and the anvil, the rest of the auditory ossicles vibrate too.
What do you think will happen to the vibrations when they pass through the small
pocket in the middle ear where the auditory ossicles lie? Will they increase or
decrease? Explain your answer.


_
round
window
stirrup
hammer
anvil
oval window
ear drum
external
anditory canal
Middle Ear
14
Ask one of your friends to go outside
with you. Ask him or her to stand 10
meters or more away from you, like in the
picture on the right. Tell him or her how
beautiful the day is. Did he or she hear
you? _ Yes _ No
Why? _


Maybe he/she heard you, but did he/she hear you clearly? Maybe not, right? He/
She may even have asked you to repeat what you just said.
Try telling him/her the same words inside
a small room. Did he/she hear you clearly?
_ Yes _ No
Why?
_
_
_
_
The correct answer is yes. The same principle applies to the way your ear works.
Since the vibrations pass from a relatively large part of the eardrum through the chain
of bones, which have a smaller area, their force is concentrated. This concentration
amplifies, or increases the vibrations.
When the vibrations reach the stirrup, it (stirrup) pushes in and out of the oval
window. This begins the function of the inner ear.
Let’s Study and Analyze
The inner ear consists of a cochlea and
three semicircular canals. These structures are
filled with fluid.
The cochlea is the coiled structure or the
shell-like structure inside your ear. It is a small
bone filled with liquid. Its function is to convert
sound waves to impulses that are transmitted by
the auditory nerve to the brain.
Inner Ear
semicircular
canal
cochlea
stirrup
15
You have learned that when the sound
vibrations reach the stirrup, the stirrup
pushes in and out of the oval window.
Thus, as the middle ear begins to vibrate,
the cochlea begins to vibrate too. When it
vibrates it makes the liquid inside it
vibrate too. The vibrations of the liquid
tickle the tiny hairs lining the cochlea,
causing them to vibrate and send a
message to the auditory nerve. The nerve
also acts like an electrical wire that sends
the messages to your brain. The tiny hairs
are part of the organ of corti.
Remember, we hear through vibrations. When the brain receives the sound
message, again, it figures out what the sound is, what is making the sound and what
you should do about it.
Do you have any idea what makes you keep your balance?
_

_
Deep in your ear are three tubes connected to a chamber. These tubes are called
the semicircular canals. These canals have no function in hearing but are involved in
maintaining balance. They lie in three different planes and are arranged at right angles
to one another. They help control balance because they are sensitive to changes in
movement and direction.
Why do you get dizzy when you ride a vehicle or a boat?
_

_
As the vehicle or boat moves, its motion tends to upset your balancing system,
thus, making you feel dizzy. Changes in the tilt of the angle of the body are sensed by
the chamber. Irregular motions can disturb the normal functions of the semicircular
canals and might result in motion sickness.
cochlea
organ of corti
Inner Portion of the Cochlea
16
Let’s See What You Have Learned
A. Give comparisons between the following pairs of objects.
1. The pupil and the opening of a camera



2. The auricle and a seashell



B. Matching Type. Match the illustrations in Column A with the descriptions in
Column B. Write the matching letter in Column B on the line before the
number in Column A.
Column A Column B
Eyes
_ 1. a. The pupil widens to let the
light enter the inner part of
the eye. The lens focuses the
image to make it clearer. An
inverted image appears on the
retina.
_ 2. b. Light-sensitive cells absorb
light rays and change them to
electrical signals. These
electrical signals then
travel along the optic nerve
to the brain.
_ 3. c. The eyes receive light rays
that are reflected from an
object.
17
Ears
_ 4. a. The fluid within the cochlea
begins to move. The hair or
nerve endings of the organ of
corti are tickled by the
movement of the cochlea.
The nerve impulses are
transmitted to the brain.
_5. b. Sounds are collected
by the auricle and travel
along the external auditory
canal. They then hit the
eardrum, causing it to vibrate.
c. The eardrum vibrates, causing
the auditory ossicles to
_ 6. vibrate too. The stirrup
pushes the vibration to the
oval window.
Compare your answers with those in the Answer Key on page 52.
Let’s Remember
♦ The eye is the organ of vision and light perception. The sense of sight helps
us recognize each other and learn about the things that we see around us.
♦ The ear is the organ for hearing and balance. The sense of hearing helps us
recognize sounds.
♦ The eye is composed of many parts. It has three layers of cells: the sclera,
choroid and retina.
♦ The eye functions through a series of steps.
• First, light rays that are reflected from objects enter the eye through an
opening called the pupil.
• Then, the lens focuses the inverted image at the back portion of the eye
that is called the retina.
18
• Inside the retina are light-sensitive cells — the rods, which identify
black and white colors; and the cones, which are sensitive to bright light
and can identify other colors.
• These cells transform light rays into electrical signals.
• These electrical signals then pass along the optic nerve to the brain.
• When the cells reach the brain, the brain interprets these electric
signals, thus enabling us to identify the objects we see around us.
♦ The ear is composed of many parts, too. It has three regions: the outer,
middle and inner ear.
• The outer ear is composed of the auricle and the external auditory canal
that extends up to the eardrum.
• The middle ear is composed of a small bone pocket that contains the
three smallest bones of the body — the hammer, anvil and stirrup.
• The auricle collects sounds from the air. The sound travels along the
external auditory organ and strikes the eardrum.
• When the eardrum vibrates, so will the three small bones in the middle
ear. The vibrations then pass through the oval window to the cochlea.
• Inside the cochlea are short hairs of the organ of corti. The vibrations
stimulate these hairs. The cells in the hairs then transform the
vibrations into nerve impulses.
• These nerve impulses are transmitted to the brain. The brain interprets
these impulses, thus enabling us to recognize sounds.
19
LESSON 2
The Organs of Smell, Taste and Touch
You have learned about the organs of sight and hearing in Lesson 1. In this
lesson, you will learn about your other sense organs — those of smell, touch and
hearing. You will also learn their different parts and functions.
After you finish studying this lesson, you should be able to:
♦ identify the different parts of your nose, tongue and skin; and
♦ explain how they function.
Let’s Try This
Do the following activity with a partner.
Get any of the following groups of liquids:
♦ clear liquids (water and alcohol)
♦ colored liquids (soy sauce and coffee)
♦ two kinds of oil (baby oil and cooking
oil)
Ask your partner to pour the liquids in a
clear container or glass.
How can you identify the liquids? What part of your body should you use to
identify them?
_

_
If you answered that you can identify the liquids by smelling them with your nose,
you are correct!
Let’s try another one. Get a matchstick (posporo).
Light it, then describe what happens.



20
Did you smell anything? How did the matchstick smell?
_
_
The matchstick burns, right? And as it burns, you can smell smoke. As the
smoke enters your nose you can smell the matchstick burning. The matchstick
produces a burnt odor. Were your answers similar with mine? If so, very good!
Let’s Study and Analyze
Can you name some things or objects with pleasant odors? If so, list them below.
_
_
Now, list things and objects that you do not want to smell because they stink or
smell bad.
_
_
The sense of smell is very important to a person. Our nose helps us know more
about the world we live in than we do when we just touch things and people or just see
them. It helps us recognize odors.
Do you have any idea how the nose works? If so, write your idea below.


Our nose, like our eyes and ears, has parts that enable us to smell many things.
The sense of smell starts with your nose, but it includes other parts of your head
and your brain.
The nose is both a sense organ for smell and a respiratory organ (organ for
breathing) of the body. It is located between the eyes.
The outer portion of the nose is
composed of bone and cartilage, a tough
flexible tissue attached to the bones. The
inner portion is hollow. It is called the nasal
cavity. A wall divides the nasal cavity. Thus,
you see two holes in your nose. The two
holes are called nostrils and the wall that
divides the nasal cavity is called the septum.
nostrils
septum
Outer Portion of the Nose
21
The nostrils are the openings of the nose. These are the parts of your nose where
the air you breathe passes.
Have you ever wondered why there are short and tiny hairs inside your nose?
What do you think these hairs are for?


The inner portion of the nose is
always wet because of mucus, the
sticky liquid inside your nose. Inside
the nose is a wet and thin lining of
tissue called the mucous membrane.
The mucous membrane is where the
fine hairs called cilia are found. These
fine hairs filter dust and other
impurities that enter your nose when
you inhale. Thus, they help ensure that
the air you breathe in is clean or free from impurities when it enters your lungs. The
air is also moistened as it passes over the sticky nasal membrane.
How can the nose detect odors?
You know that your nose is the organ responsible for your sense of smell. The
part of the nose that is responsible for smelling actually lies in the mucous membrane
on the upper portion of the nasal cavity near the septum.
It is made up of
olfactory cells (olfaction is
the other word for smell).
These cells are actually nerve
cells that function as
receptors for the sense of
smell.
These cell receptors are
called the olfactory nerve
receptors. The olfactory
nerve receptors generate
nerve impulses in response to
chemicals in the air. These impulses are brought to the brain by the olfactory nerve
fibers.
The olfactory nerve fibers are the free ends of the olfactory nerve receptors.
These fibers are buried in the mucus that coats the inner surface of the nasal cavity.
They are stimulated by various odors carried by the air you breathe.
Nerve fibers extend from the olfactory cells to an area of the brain called the
olfactory bulb. From there, the impulses are brought to the other parts of the brain
where they are made into sensations of smell.
mucous
membrane
cilia
nostrils
nasal
cavity
olfactory
bulb
mucous
membrane
AIR
olfactory
nerve fibers
olfactory
nerve
receptors
Air Passage Inside the Nose
Inner Portion of the Nose
22
Let’s Think About This
Let’s go back to the burning matchstick. Explain how you were able to smell it
using what you have just learned about your sense of smell.
_


Compare your answer with the one given below.
Using the burning matchstick as an example, you can understand more how your
sense of smell works.
When the matchstick started to burn, tiny particles of ash that came from the
match floated in the air. These small pieces of material are too small for you to see,
but the nose is sensitive to them and can smell them as they travel in the air into your
nose.
When the small pieces of ash “tickle” the nerve endings of the olfactory nerve,
the olfactory nerve carries the message to your brain, telling it that you are smelling a
burning matchstick.
Let’s Review
When you have colds and your nose is all stuffed up, why can’t you smell
something like perfume?

_
_
Compare your answer with that in the Answer Key on page 52.
Let’s Study and Analyze
The tongue is the main part of the body you use for tasting food. It carries
messages to the brain about the taste of what you are eating.
Inside your mouth are small bundles called taste buds. These are groups of
sensory cells with many nerve endings, just like the nerve fibers in your nose. They
detect the taste of the food you are eating or the fluid you are drinking.
Taste buds are stimulated by chemicals that dissolve in the saliva. The four kinds
of tastes are salty, sour, sweet and bitter.
23
Let’s Try This
Get a pinch of salt, some sugar, some powdered coffee, and calamansi.
Do you know how each one tastes? If so, write their tastes below.
a. salt =
_
b. sugar =
_
c. coffee =
_
d. calamansi =
_
Dry your tongue with a clean towel. Put a small amount of salt in your tongue.
Were you able to taste anything?
_ Yes _ No
Try doing it again, this time with sugar, then coffee, then calamansi.
Were you able to taste anything?
_ Yes _ No
Not very much, right? What could be the reason for this?
_
_

There is another important thing to remember about the sense of taste. It is the
saliva or the sticky fluid in your mouth that helps you taste your food. The saliva
mixes with the food and spreads the flavor all over the tongue. The different taste
buds then begin their jobs and you can tell if the food or liquid is sweet, sour, salty or
bitter. If your tongue is dry or if there is no saliva in your mouth, this process will not
take place. As a result, you wouldn’t be able to taste anything you eat or drink.
Let’s Learn
Did you know that specific tastes are perceived or “tasted” only by certain areas
of the tongue?
You learned that on the surface of the tongue are small bundles of nerve endings
or taste buds, right? The taste buds are grouped into four regions on your tongue.
Each region perceives a certain taste, be it sweet, sour, salty or bitter. The regions are
as follows:
♦ Sweet tastes are perceived on the middle and tip of the tongue.
♦ Salty tastes are perceived at the tip and edges of the tongue.
24
♦ Sour tastes are perceived on the sides of the
tongue.
♦ Bitter tastes are perceived at the back of the
tongue.
Will you be able taste a green mango if it only makes
contact with the middle part of your tongue? Explain your
answer. _
_
_
If you answered no, you are correct! You won’t be able to taste the sourness of
the green mango if it only makes contact with the middle portion of your tongue. It
should make contact with the sides of your tongue for you to be able to taste it.
Let’s Think About This
Is the smell of your food important to you? If you have colds, can you taste your
food well?
_ Yes _ No
Why do you say so?

_
_
If your answer is no, you are correct!
Look at the illustration on the right.
The senses of taste and smell often
function together. If your nose is blocked
you will have a difficulty distinguishing
certain flavors that you actually smell
rather than taste.
Your senses of smell and taste are also
known as chemosensory organs. The
olfactory cells that detect odors and the
gustatory cells (cells found in the nerve
fibers of your taste buds) that perceive
tastes are both sensitive to chemicals that
you smell and taste.
Your surroundings, including the foods you eat or the liquids you drink, all release a
certain amount of chemical particles in the air. The tiny particles enter your nose and
stimulate the sensory cells, specifically the olfactory cells of the nose. These cells
transmit the messages to your brain where specific smells are identified. The same thing
applies to our sense of taste. The taste buds on the surface of your tongue are sensitive
to chemicals in your food. The gustatory cells detect the taste of food.
tongue
nerve to the brain
olfactory
cells
nerve to
the brain
gustatory cells
bitter
sweet
sweet
and salty
s o u r
s
o u r
25
Let’s Review
Are you often tempted to eat something that smells good, spaghetti, for example?
Why?

_

When you smell food, you can easily recognize how it tastes especially if you
have tasted it before. When you smell the spaghetti, we already know that it tastes a
little bit sweet, sour and salty.
Let’s Try This
Do you think your sense of touch is important? Why?



If you answered that it is important, very good! Your sense of touch is very
important because it enables you to do a lot of things.
What could possibly happen to you if you can’t feel anything? Will you still be
able to do—with ease—the things that you usually do, like drinking water, eating and
doing household chores? How will you be able to hold the glass, spoon or the fork if
you cannot feel that you’re holding it?
Do you know what your sense of touch is and how it works? Do the following
activities and answer the questions.
1. Place your palm on the table and stand on the floor barefooted. Be sure to
stand firmly on the ground. Can you feel anything? Describe how you feel.
_
_
_
2. Put your bare foot into a washbasin (palanggana) with lukewarm water.
What do you feel? Can you feel something wet and something rough at the
same time? Explain why.
_
_
_
26
3. Ask a friend or co-learner to collect stones and objects of different sizes
and shapes. Tell him/her to put them inside a bag or box. After your partner
finishes his/her task, try to identify each object inside the box or bag without
looking at it. Were you able to identify them all? How were you able to
identify the objects if you can’t see them?
_
_
_
Compare your answers with those in the Answer Key on page 52.
Let’s Study and Analyze
Can you identify an object just by touching it? How about the blind, how can they
read if they cannot see what they are reading?
The sense that notifies contact with an object is the sense of touch, also called
the tactile sense. Through this sense, you know the shape, hardness or temperature of
objects. You can also feel pleasure, pain and pressure through the sense of touch.
The sense of touch is very important because you use it in several ways. Its main
organ is your skin. Your nails and hair are also organs of touch.
Can you list down below all the uses of your skin that you can think of?

_
_
Do you know that the skin is the largest organ of your
body? In an adult, the skin could measure up to 20 square feet.
It is the giant, stretchable, washable, and waterproof covering
of your body that keeps your internal organs in!
Your skin covers all of your body. It protects you from
heat and cold and disease-causing bacteria. It also gives you
information about what is around and outside your body. When
you touch something your skin tells you if that thing is wet or
dry, hot or cold, rough or smooth, hard or soft.
The skin can give you a lot of messages about your
surroundings all at the same time. Remember what you did
earlier? When you touched the top of the table and stood
barefoot on the ground, you felt the roughness or smoothness
of the table and floor, didn’t you? You were also able to tell if
the table and floor were warm or cold, right?
27
Let’s Think About This
Will you touch a hot object or not? Why?
_
_
_
How will you know that it’s hot?
_
_
_
Most probably, you will not touch an object when you know that it is hot. Or if
you do not know that the object is hot, you will remove your finger or any part of the
body immediately from the hot object, as soon as you touch it.
The sense of touch provides a warning when there is a threat to the body. Pain is a
signal that we need to act immediately so that we could avoid damaging our body.
Without your sense of touch you might burn yourself without knowing it and accidents
might happen to you.
Can you list some accidents that might happen if you lost your sense of touch?
Write them down below.
_
_
_
Here are some of the accidents that might happen if you lost your sense of touch:
♦ The things you hold always has a tendency to drop because you tend to forget
that they are in your hands;
♦ You can’t feel pain, even if you wound yourself; and/or
♦ You get the different parts of your body burned
Let’s Learn
You feel different sensations when you come in contact with objects because of
your touch organs. There are many kinds of touch organs in the skin and mucous
membranes. These touch organs are found near the hairs, in hairless areas and in
deeper tissues.
You have learned that your senses of smell and taste are made possible because
of nerve endings that act as receptors. These nerve endings send messages to your
brain. It is the same with your skin. Below the skin are intricate networks of nerves
that also send messages to the brain.
28
Have you ever experienced numbness when you sit on
your feet for a long time?
Sensations are measured below the skin by the nerve
fibers or nerve endings that act as receptors. They tell your
brain how to respond.
When you sit on your feet for a long time, the weight
of your upper body squashes your nerves and blood vessels.
When you feel the tingling sensation it just means that your
nerves want you to know that they are numb.
Below your skin are layers of tissue, called the
epidermis and dermis.
The epidermis is the outermost layer of the skin. It is the visible part of your
skin. The next layer of skin is the dermis. This is made up of blood vessels and nerve
endings.
If you look closely at the illustration of the skin you will see that there are
different kinds of nerve endings or receptors. These nerve endings respond
differently. Some receptors respond to pressure, some to temperature and others to
pain.
sweat
gland
epidermis
dermis
29
Let’s See What You Have Learned
Fill in the blanks with the correct answers. Then, find the answers in the puzzle
that follows. The words may be found horizontally, vertically or diagonally.
1. The
is the outermost layer of the skin.
2.
is another term for smell.
3.
is the sticky fluid in the mouth that dissolves
the food we eat. It spreads the flavor of the food we eat to our taste
buds.
4. The
is the inner portion of the nose. It is
hollow.
5.
are nerve endings or fibers that send
messages to the brain.
6. The
is the organ for taste.
7. The
is the wall that divides the hollow
portion of the nose.
8.
is another term for the sense of touch.
9. Your senses of smell and taste are also known as
_
organs because they are sensitive to the chemicals that we both inhale
and taste.
10.
is the taste perceived in the middle and at the
tip of the tongue.
11.
are the fine hairs found inside the nose.
12. The
is the main organ for the sense of touch.
13.
are groups of sensory cells with many
nerve fibers that detect the taste of the food we eat.
14. The
is the inner layer of the skin. Nerve
fibers and blood vessels are all around this layer.
15.
is the taste perceived at the back of the
tongue.
30
Compare your answers with those in the Answer Key on page 53.
Let’s Remember
♦ Your nose, tongue and skin have many parts that enable you to smell, taste
and feel.
♦ When odors enter your nose, nerve sensors (nerve endings in the mucous
membrane) inside the nose are stimulated. These sensors send messages to
the brain.
♦ On the surface of the tongue are thousands of taste buds that detect the
tastes of the foods you eat. On each taste bud are nerve endings that send
messages to your brain.
♦ Your tongue is divided into four regions. Each region detects one of the
four tastes: sweet, sour, salty and bitter.
♦ Your skin is the outer covering of your body.
♦ It has layers, namely, the epidermis (outer layer) and the dermis (inner
layer).
♦ In the dermis are nerve endings that detect pressure, temperature, pleasure
and pain.
N A S A L C A V I T Y R S T R
T S D F D T S D C X Z X A E U
A D J K E I O K E R G H C V B
C F H E E C V B I I J E H D N
T G W L J K P O I N P P J E O
I S D U B E T S A T T I U R I
L M N J K L O P O R F D I S T
E Y T E A S D R R I G E P Z C
W M U T P E S D F B H R O D A
S H J O T R F A D E R M I S F
A I U N Y F I P L N M I L A L
I O P G Y U I O G I L S K S O
L K L U P L K J H B V K J D I
I M R E T T I B N N N A M F H
C H E M O S E N S O R Y S G B
31
LESSON 3
Sensory Diseases and Their Prevention
In the previous lessons, you learned about the importance of your sense organs to
your daily life. Your sense organs help you do so many things. You learn about the
outside world through them. The loss of any one of your senses will immensely affect
the way you live, move and interact with people. If any disease affects your senses, it
will be very hard for you to go about your usual activities.
In this lesson, you will learn about the different diseases that may affect your
sense organs. If the parts and functions of the sense organs discussed in the previous
lessons are not clear to you, I suggest you review them first before studying this
lesson. It is important that you are familiar with how your sense organs work before
you start this lesson.
After completing this lesson, you should be able to:
♦ cite some of the common diseases related to the sense organs;
♦ enumerate the signs and symptoms associated with each disease; and
♦ tell how these diseases can be prevented and cured.
Let’s Read
Your eyes play a very important role in your life. They enable you to see your
surroundings.
Read the following dialogue.
On his way home from the farm, Jerry met his friend Tony.
Jerry : What happened to your eyes, Tony?
Tony : I contracted conjunctivitis or sore eyes.
32
Jerry : Isn’t that contagious?
Tony : Yes, it is.
Jerry : How did you get sore eyes?
Tony : The doctor said that you can get sore eyes anywhere. I think I got this
from the market where there are a lot of people. Someone who has
sore eyes may have rubbed his/her eyes and touched something that I
also touched. I rubbed my eyes without washing my hands, and there, I
got the disease.
Let’s Try This
Answer the following questions based on what you have learned from the
dialogue.
1. What is conjunctivitis?
_
2. How did Tony get it? _
_
_
3. How can conjunctivitis be prevented?
_
_
Compare your answers with those in the Answer Key on page 53.
Let’s Study and Analyze
Have you ever had an eye disorder?
Nowadays, if you are not careful, you may get an eye disease. Did you know that
some eye diseases that are not treated immediately and properly may lead to
blindness.
Listed below are some common eye diseases that need immediate treatment:
1. Conjunctivitis (sore eyes). This is also
known as “pinkeye” because of the inflamed
or swollen tissues or mucous membrane that
lines the back of the eyelid. It is the most
common infectious disease that affects the
eyes, especially the eyes of children.
33
Have you ever had conjunctivitis? _ Yes _ No
If yes, can you still remember its symptoms? List them below.


The symptoms of conjunctivitis are as follows:
♦ The first symptom is discomfort or itching and excessive watering of the
eye.
♦ This is followed by redness and inflammation (swelling) of the conjunctiva
and the inner surface of the eyelids. There may be some pain accompanying
the inflammation, but the person who has conjunctivitis might probably
complain more about the discomfort in the eye. A person with
conjunctivitis has the tendency to rub the eyes mainly because of the
discomfort and itchiness experienced there.
♦ After a day or two, a yellowish-white (sometimes light green) discharge may
appear around the eyes (pagmumuta).
How did you treat your sore eyes?


What could possibly happen to your eyes if you rub them?


When a person has a sore eye or conjunctivitis, he/she should not rub the
infected eye because the disease may transfer to the other eye. He/She should also
wash his/her hands often and use separate towels so as not to spread the disease to
other people. Although most types of conjunctivitis are contagious, it usually causes
no danger to the eye or to the vision. However, conjunctivitis caused by bacteria is
infectious. The discharge (muta) will somehow be thicker. If this happens, consult
your doctor immediately because bacterial conjunctivitis can also cause ear
infections.
2. Sty (kuliti). This is another common disease
of the eye. It is a small abscess of the tissue
in the eyelids near the root of an eyelash. A
person may get more than one sty at a time.
Have you ever heard the old belief about
sties?
Have you ever had a sty?
_ Yes _ No
34
If yes, did your friends laugh at you? If yes, why?

_
It is an old belief that a person gets a sty as a punishment for peeping at a naked
person (pamboboso).
However, to be scientific, a sty is a bacterial infection caused by the
staphylococcus bacteria.
Its symptoms include swelling, redness and pain. When the inflammation bursts,
the pain is relieved, and there is immediate improvement.
To treat the sty, bathe it repeatedly with a clean cloth soaked in hot water. If it
does not burst by itself, visit your nearest health center for assistance.
3. Sometimes, a foreign body gets lodged in the eye (puwing). If the foreign
body is soft, instruct the person to close his/her eyes. Lead him/her to a
bright place and tell the person to open his/her eye gently.
Look for the object that lodged in the eye. When it is located, get it out of the
eye by lifting the particle with the moist corner of a handkerchief.
If the foreign body is stuck in the white of the eye, seek professional help at
once. Do not try to remove the object by yourself.
Aside from what were mentioned, there are more disorders that may affect the
eye. Some are listed below:
Farsightedness (hypermetropia) — distant things are seen clearly while
objects at close range are blurred. Corrective glasses or contact lenses are
prescribed to correct the disorder.
Nearsightedness (myopia) — distant objects are blurred while objects at
close range are seen clearly. Eyeglasses or contact lenses can also correct
this eye disorder.
Night blindness (ocerphthalmium) — This disorder may occur if there is a
dietary deficiency of vitamin A. Vision is not clear in dim light or at night.
Night blindness also occurs in patients with eye disorders called
choroidoretinitis and glaucoma.
Let’s Review
Answer the questions below.
1. One of your brothers/sisters has conjunctivitis. What must he/she and all of
you in the family do to prevent the spread of the disease?
_
_
_
35
2. Lina has a sty. Should she prick her sty with a needle to drain all the pus
(nana) inside it? Explain your answer.
_
_
_
Compare your answers with those in the Answer Key on pages 53–54.
Let’s Read
You learned about the importance of your ears in Lesson 1. They enable you to
hear the sounds all around you. Imagine if you don’t have ears. Do you think you will
be able to do the things you used to do?
Your ears, if not taken care of properly, can easily be damaged. They are very
important and sensitive sense organ. To learn more about ear disorders, read the
following dialogue.
At the health center . . .
Jun: Good morning, Doctor.
Doctor: Good morning, Jun. What can I do for you?
Jun: Doc, last week I had a very bad cold. This morning, I woke up with a
very painful left ear.
Doctor: Let’s take a look at it.
Doctor: You have otitis media in your left ear. It’s good that you have come at
once to consult me.
Jun: Doc, what’s otitis media?
Doctor: Otitis media is an inflammation of your middle ear. If not treated
immediately, it can lead to deafness.
Jun: So how can it be treated?
36
Doctor: I’ll give you a strong antibiotic and an antihistamine to relieve the
blockage.
Jun: Thank you very much, Doc. I’ve got to go now.
Doctor: Anytime, Jun.
Let’s Think About This
From what you have just read, what is otitis media?
_


How did Jun acquire otitis media? What are its symptoms?
_


How can it be treated?
_


Have you finished answering the questions? If so, you can compare your answers
with the following discussion.
Otitis is an inflammation of the ear. When it occurs in the outer ear, or the
auricle, it is called otitis externa. When it occurs in the middle ear the inflammation
is known as otitis media. The inflammation of the inner ear is called labyrinthitis.
1. Otitis Externa. This is more commonly known as “swimmer’s ear.” It is an
infection of the ear canal (external auditory canal). The ear canal is naturally
acidic. The acid prevents bacteria from living in your ears.
When a person swims frequently, the water enters the ear and washes
out the acid in the canal. This allows bacteria to thrive in the ear. It can be
caused by a combination of bacterial and fungal infections caused by
scratching of the ear, swimming or excessive sweating.
Symptoms Treatment
Itching, pain in the ear, slight
discharge, deafness. An
abscess (boil) may form.
1. Use earplugs whi
2. Take prescribed m
3. Avoid scratching
37
2. Otitis Media is an infection of the middle ear. It occurs very frequently in
children, especially those under five years old.
Middle ear infections occur when the tube that connects the back of the
nose to the middle of the ear does not function well. The job of this tube is
to allow air to pass from the nose to the middle ear. When it is not working
well, a build-up of fluid may occur in the middle ear. If this happens, the
fluid that has accumulated in the middle ear will then serve as an
environment for bacteria to grow and an infection to occur. The middle ear
is supposed to stay dry.
Have you ever experience having a whooping cough that caused your
throat to ache? _ Yes _ No
If it happened to you, was your ear painful afterwards? If so, what could
be the reason for this?
_
If that happened to you, you might have had otitis media. This means that
your eustachian tube had become swollen. The swelling of the tube had
blocked the air from entering your middle ear. Then, fluid had built up in the
middle ear, instead of draining out into the throat.
3. Labyrinthitis is an inflammation of the semicircular canals in the inner ear.
Can you still remember what you have learned in Lesson 1? The
semicircular canals are fluid-filled chambers that help you keep your
balance, right? If you damage them, it would be really difficult to maintain
your posture.
Labyrinthitis is a bacterial infection that might result from otitis media,
from meningitis or occur after an ear operation.
Symptoms Treatment/
Severe earache,
decreased hearing, fever,
pus
Young children may have
diarrhea, stomach pain
and vomiting.
1. Use prescribed antibiotic
painkillers.
2. Keep ear clean and dry,
has ruptured.
Symptoms Treatment/
- extreme dizziness
that begins gradually
and peaks in 48
hours
- involuntary eye
movement
- vomiting
- loss of balance
- hearing loss
- ringing inside the
ears
1. If you experience the sy
medical treatment imme
2. Don't take any medicatio
by an ear specialist.
38
Let’s Review
Identify what ear disorder is being described in the following sentences.
_ 1. A person hears a ringing inside his/her ear, which is
accompanied by dizziness and vomiting.
_ 2. This ear disease is acquired when a person suffers from
severe colds. Earache and fever can accompany this
disease.
_ 3. This ear disease makes a person lose his/her balance.
_ 4. This ear disorder develops from an infection caused by
bacteria when fluids build up inside the ear.
_ 5. This ear disease develops when the natural acids of the
ear are washed away, thus giving disease-causing
bacteria a chance to live in the ears.
Compare your answers with those in the Answer Key on page 54.
Let’s Try This
Can you still remember what you have learned in Lesson 2, that is when you have
clogged nose, you can hardly smell anything? Your sense of taste did not function
very well either, right?
Imagine yourself permanently incapable of smelling the things around you and
tasting the food you eat. Will you still be able to enjoy your life and do the things that
you are used to do? Explain your answer.



There are a lot of things that you will not be able to do if you lose your senses of
smell and taste. You won’t be able to taste what you eat. You won’t know whether the
food you eat tastes good or bad. Much worse, you might eat spoiled food without
knowing it. This is because you will be unable to taste and smell your food.
Smell and taste problems can have a big impact in our lives. These senses
contribute significantly to our enjoyment of life, our desire to eat, and the way we
deal with people. Smell and taste disorders can be serious. When your senses of
smell and taste are impaired, you eat poorly and socialize less.
39
What’s the first thing you do when you smell something
burning?



Most probably the first thing you do is find out where the odor came from, right?
Your senses of smell and taste can warn you about dangers such as fire, poisonous
fumes and spoiled food.
What can possibly cause you to lose your senses of smell and taste?



The loss of smell and taste may be caused by polyps (masses of swollen
membrane in the nasal cavity), hormonal disturbances (especially for females because
of the menstrual cycle), dental problems or diseases of the tongue.
Have you ever entered a newly painted room? If so, what was the first thing you
did?



I’m sure, the first thing you did was cover your nose, right? Do you know why you
automatically cover your nose when you smell something bad? This is because your
nose easily gets irritated by foul odors, especially toxic chemical substances.
What do you think will happen to your sense of smell if you inhaled too much
chemicals like solvents (liquids mixed with paint)?



Prolonged exposure to certain chemicals such as insecticides and solvents can
result to the loss of your sense of smell.
40
Let’s Learn
Disorders of smell can be classified as either hyposmia (a decrease in
sensitivity) or anosmia (the complete absence of smell).
There are many other causes of smell malfunction besides the ones mentioned in
the earlier activity. Some of these are:
♦ Respiratory disorders such as nasal
infections and constant allergies and colds.
These conditions can block the flow of air.
Isn’t it that when you have colds you
experience difficulty in breathing? Why is this so?



When you have a cold, the mucous membranes inside your nose swell
(namamaga) and the amount of mucus produced increases. When this happens, your
sensitivity to odor decreases. Allergies and rhinitis (an infection of the olfactory
membrane) may also cause a loss of smell.
You have learned in Lesson 2 that your
nose has tubes in it, right? If these tubes are
stuffed up due to a common cold, you will
experience difficulty in smelling because
odors are prevented from reaching the smell
receptors or nerve fibers. Because the ability
to smell affects taste, food often doesn’t taste
right when you have colds.
♦ Viral infections or toxic destruction
(solvents and gases), heavy metals
and various kinds of industrial dust
can also damage your sense of
smell. This kind of disorder is
rarely cured.
♦ The most common cause of
permanent loss of sense of smell is
head trauma. In this case, fibers of
the olfactory nerves that send
messages to the brain are damaged.
♦ Smoking can also damage your
ability to identify odors and can thus
reduce your sense of taste.
41
Let’s Study and Analyze
Another common nose disorder that can cause a temporary loss of smell is the
nosebleed. One or both nostrils may bleed, usually as a result of a local injury or
disturbance inside your nose.
Most nosebleeds are not serious and occur when one of the small veins of the
septum ruptures. This will usually stop without treatment or when pressure is applied
to the nose.
Bleeding may also be caused by an infection (like the common cold), a blood
disorder (leukemia or hemophilia), frequent picking of nose with untrimmed
fingernails, high blood pressure or an abrupt change in temperature. Persistent
nosebleeds should be brought to the attention of a physician.
When the nose bleeds, tell the victim to
sit down with the head tilted upward while
pinching the nose. Hold it for five minutes
until the bleeding stops. If bleeding does not
stop within 30 minutes, seek professional help.
Place a gauge pad or any clean cloth in each
nostril. The victim should breathe through the
mouth.
Let’s Try This
Answer the following questions. Write your answers in the spaces provided.
1. What are some of the disorders that can affect your sense of smell?
_
_
_
2. How can smell disorders be prevented?
_
_
_
Compare your answer with those in the Answer Key on page 54.
42
Let’s Study and Analyze
You have just learned that your sense of smell is connected with your sense of
taste. If you have a smell disorder, most likely, you also suffer from a taste disorder.
If the sense of smell has disorders like hyposmia and anosmia, the sense of taste can
be affected by disorders like ageusia (reduce or loss of taste) and dysgeusia
(distortion of taste).
If a person has ageusia, he/she usually cannot taste food that much, or worse, he/
she cannot taste food completely. Aguesia is usually caused by conditions that affect
the tongue. Examples of these conditions are: a dryness of the mouth, heavy smoking,
radiation treatment of the head and side effects of medicines and drugs.
Can you still remember what you learned in Lesson 2 about your tongue? We
discussed that it is always wet. What’s the reason for this again? What will happen if
your tongue becomes dry?
_

Your tongue is always wet because your saliva helps dissolve the food you eat and
spread the flavor to the rest of your tongue. If your tongue becomes dry you wouldn’t
be able to taste the flavor of the food you eat.
A person who has dysgeusia, on the other hand, has
difficulty tasting food correctly. For example, candy
might taste sour for a person who has this disorder.
Dysgeusia may be caused by the same conditions
that cause ageusia.
Do you think smoking can harm your sense of taste?
Explain your answer.
_

If your answer was yes, you are correct! Smoking and radiation burn the taste
receptors in the tongue. Burns on the tongue may temporarily destroy the taste buds.
What will happen if your taste buds are destroyed?
_
_
In Lesson 2, you learned that your taste buds enable you to taste the flavors of the
food you eat. They are the taste receptors of your tongue. If your taste buds are
destroyed, you will not be able to taste food correctly. For example, if your taste
buds for sweet flavors are damaged, then you will not be able to taste the sweetness of
food.
43
Let’s Learn
There are different diseases that can affect the tongue and that can affect a
person’s sense of taste. Listed below are some of these.
singaw or herpes simplex — This is also called cold sore or fever sore. It
results when another infection occurs, like the common cold. Other causes
of singaw are stress or exposure to wind, sunlight, certain foods or drugs and
for women, the menstrual cycle.
Herpes simplex has no symptoms. It usually appears around the lips and
nose as a small blister and becomes an ulcer later on. Alum (tawas) or
aluminum hydroxide (for stomach ulcers) can treat herpes simplex.
glossitis or inflammation of the tongue — The symptoms of glossitis
include pain, sometimes an ulcerated tongue, sticky and thick saliva and
difficulty in swallowing. It can be treated with antiseptic mouthwashes. To
reduce the pain the patient may be given an anesthetic solution.
Let’s Think About This
Do you think your sense of touch is as important as your other senses? Why or
why not?
_
_
_
If the loss of your senses of smell and taste can make things very difficult and
inconvenient for you, what more if you lose your sense of touch and become unable
to feel anything? Do you think you can still do the things that you used to do? Your
sense of touch is very important. Without it, how will you know if your hands get
stuck in a door, or if somebody pinched you and pulled your hair? How will you be
able to hold something? You might break a glass if you hold it too firmly or you might
drop it if you hold it too loosely. How will you know if you’re holding it right?
Because your sense of touch is very important to your everyday life, you need to
take good care of the organ responsible for your sense of touch, that is, you need to
take good care of your skin.
How do you take care of your skin?
_
_
44
Among the many things you can do are:
♦ take a bath everyday;
♦ change clothes regularly;
♦ trim your nails regularly;
♦ avoid being exposed to too much heat; and
♦ avoid insect bites.
What would happen if you do not take care of your skin?
_
_
If you do not take good care of your skin, you become susceptible to skin
diseases such as allergies. Read the next dialogue to learn more about skin diseases.
Let’s Read
Have you ever had a skin disease before? If so, can you list down what type it was
and the ill effects it gave you in the spaces below?
_

Read the following dialogue about skin diseases.
Ben : Hey, Oscar, why don’t you sit properly?
Oscar: (whispering) Pare, I have a boil on the left part of my butt.
Bernie, Ben, Paul: Ha-ha-ha!
Ben: What actually caused the boil?
45
Oscar: The doctor said that boils are caused by bacteria called
staphylococcus. The bacteria infect the hair roots or the glands
where our sweat comes from.
Bernie: Boils are painful. I once had a boil under my arms. It really hurt.
Paul: Where else can boils develop?
Oscar: My doctor said that boils develop in areas where the skin is constantly
rubbed, like at the back of the neck, around the groin, on the thighs
and behind the knees.
Ben : So, what did the doctor tell you to do?
Oscar: He told me to soak a clean cloth in warm water and apply it repeatedly
on the boil.
Paul: What will that do?
Oscar: It will hasten the development of the head of the boil. When the boil is
ripe, it will drain on its own.
Paul: My brother had a boil once. Our doctor told us not to cut open the boil
because the infection will spread. Since my brother’s boil was on the
face, the doctor prescribed an antibiotic. Antibiotics are also given for
boils on the nose.
Ben: What other skin disorders could we get?
Bernie: There are a lot of germs in the air we breathe and in the water we use for
bathing and drinking. We can contract skin diseases like carbuncle.
Paul: What’s a carbuncle?
Bernie: It’s like a boil. The skin is inflamed by the bacteria called
staphylococcus aureus.
Oscar: Stappp—illo-coc… what? Ah okay, carbuncle. So how do you treat a
carbuncle?
Bernie: If the carbuncle is acute, the doctor has to make an incision to drain the
pus. Antibiotics are given by the doctor.
Ben: When I was a kid, I had scabies.
Paul: Wasn’t that very itchy?
Ben: Indeed, it was. I even cried because of the itch.
Bernie: How was the scabies removed?
Ben : My mother brought me to the doctor. He prescribed a scabicide that
was applied all over my body after every bath. It was done twice a day.
I was so relieved when the scabies was treated.
46
Paul: What makes scabies itchy?
Bernie: I can answer that. I read it in a magazine only a week ago. Scabies is
caused by the itch mite called sarcoptes scabiei.
Oscar: That’s another Latin name to add to our vocabulary.
Paul: Go on, Bernie. Oscar, stop interrupting.
Bernie: Okay. The female mite burrows beneath the skin, lays eggs and forms
tunnel-like nests. The eggs turn into larvae that mature and mate.
The victim, like me, suffers an allergic reaction in the form of a very
itchy rash. Scabies is very contagious.
Paul, Ben, Oscar: Yuck!
Let’s Review
From what you have just read, complete the table below by providing the causes,
symptoms and treatment of the skin diseases discussed in the dialogue. Write your
answers inside the table.
Compare your answers with those in the Answer Key on page 54.
Let’s Learn
The friends discussed a lot of skin diseases or disorders. Below is another type
of skin allergy that you might want to add to your knowledge.
Atopic Dermatitis. This skin disease is more popularly known as eczema. It is an
itchy, dry inflammation of the skin. It is the most common type of skin disease among
children. It is usually contracted by people with sensitive skin. It usually occurs on the
face, elbows, back of the knee, limbs and torso.
Diseases Causes Symptoms
1. Boils
2. Carbuncle
3. Scabies
47
Although eczema is not an infectious disease, the skin may be severely affected
because of too much scratching. Crusting on the surface of the skin may develop when
the eczema becomes infected (especially when a person rubs his/her skin with
untrimmed and dirty fingernails).
There are many external factors which may worsen the eczema. Among these
are:
♦ Sudden changes of room temperature, strenuous exercise and hot, humid
weather
♦ Synthetic or woolen clothing. (Children should be dressed in cotton.)
♦ Emotional upsets
♦ Cigarette smoke. In an enclosed room, smokes and fumes may irritate the
skin.
♦ Furry pets. Avoid keeping cats and dogs in the house.
How can eczema be prevented? It can be prevented by avoiding the factors stated
above. It can be treated by using ointments and lotions prescribed by a dermatologist
(a doctor that specializes in skin diseases).
Let’s See What You Have Learned
Complete the table below. In Column 1, you can see the different diseases that
can affect the sense organs. In the succeeding columns, write the following:
Column 2 - The sense organ affected by the disease
Column 3 - Causes and symptoms of the disease
Column 4 - Treatment and prevention of the disease
Compare your answers with those in the Answer Key on page 55.
Diseases Sense Organ Causes/ Sy
1. Conjunctivitis
2. Otitis media
3. Dysguesia
4. Hyposmia/
Anosmia
5. Eczema
48
Let’s Remember
♦ Some examples of common eye diseases are conjunctivitis and sties.
♦ Conjunctivitis is an inflammation of the mucous membrane at the back of
your eyelid. It is a bacterial infection.
♦ A sty is an inflammation of the tip of the eyelid. It may result from dust and
dirt particles that have gotten into your eyes.
♦ To treat conjunctivitis and sties, avoid rubbing your eyes and wash them with
warm water.
♦ Some examples of ear diseases are: otitis externa, otitis media and
labyrinthitis.
♦ As a rule, always keep your ear dry because fluid inside the ear may cause
infection.
♦ The loss of the sense of smell may result from common colds, too much
exposure to toxic chemicals and head trauma.
♦ The loss of the sense of taste may result from burns on the taste buds,
hormonal imbalances and diseases of the tongue and mouth.
♦ Always keep your body clean to prevent any skin diseases.
♦ Some common skin diseases are boils, carbuncle, scabies and eczema.
♦ As much as possible, avoid rubbing your skin when itchy.
♦ If symptoms persist, consult a doctor.
Congratulations! This is the end of the module. So how was it? Did you learn a
lot? If there are some parts that are not clear to you, read them again to understand
them better.
49
Let’s Sum Up
♦ You learn about the world you live in through your senses. You learn from
what you see, hear, smell, taste and feel.
♦ The eyes function like a camera. You see objects through the light
reflected from the object. When light rays enter the eyes, the cells at
the back of the retina transform them to electrical impulses. These
impulses are carried to the brain, which then interprets these impulses as
images.
♦ Your ears collect sounds from your surroundings. You are able to hear
because of the vibrations produced by your eardrum.
♦ The nose, tongue and skin have cells that act as receptors. These receptors
are in the nerve fibers present all over your sense organs.
♦ When chemicals come in contact with the receptors or nerve fibers, as in the
case of the nose and the tongue, these nerve fibers send messages to the
brain. The brain interprets the messages as odors and tastes.
♦ In the case of the skin, the nerve fibers scattered all around the dermis are
sensitive to pressure, temperature, pleasure and pain.
♦ The loss or damage of any of your senses would mean a great loss to you.
Life would not be complete because you will not be able to do the things you
want and used to do. Thus, your eyes, ears, nose, tongue and skin are very
important parts of your body that you must take good care of.
What Have You Learned?
A. Explain how each of your organs works.
1. Eye


2. Ear


3. Nose


50
4. Tongue


5. Skin


B. Answer the following:
1. Why shouldn’t you rub your eye?
_


2. Why should you keep your ear dry?
_


3. Why should you avoid being exposed to toxic chemicals?


4. Why should you avoid smoking? _


5. Why should you always keep your body clean? _

__
Compare your answers with those in the Answer Key on pages 55–57.
51
Answer Key
A. Let’s See What You Already Know (pages 2–3)
A. 1. (c) 6. (d)
2. (b) 7. (a)
3. (c) 8. (c)
4. (b) 9. (c)
5. (a) 10. (d)
B. 1. skin
2. ears
3. nose
4. eyes
5. tongue/taste
B. Lesson 1
Let’s Review (page 7)
A welder uses dark protective eyewear or a welding mask to protect his
eyes from too much light, which can cause blindness.
Let’s Review (pages 8–9)
1. The sclera protects the eye. It is responsible for the formation of the
iris.
2. The cornea protects the lens of the eye.
3. The choroid absorbs excessive light.
4. The pupil functions as the opening of the eye. It is where the light
enters.
5. The iris controls the amount of light that enters the eye.
6. The retina is where the light rays are focused. Inside it are lightsensitive
cells that transform light rays to electrical signals.
7. The lens focuses the light rays on the retina.
8. The optic nerve transports the electrical signals from the cells of the
retina to the brain.
52
Let’s See What You Have Learned (pages 16–17)
A. 1. The pupil and the opening of the camera are both sensitive to light.
They both let the light enter into the inner portion of the eye/
camera. When the light is dim, the pupil and the opening of the
camera widen or dilate. On the other hand, when the light is
bright, the pupil and the opening of the camera narrow or become
smaller.
2. The auricle and a seashell have a similar shape. The flap of the ear
is shaped like a seashell so that it can collect more sounds from
the surroundings.
B. Eyes
1. (c)
2. (a)
3. (b)
Ears
4. (b)
5. (c)
6. (a)
C. Lesson 2
Let’s Review (page 22)
When you a cold, your nose is stuffed up with fluid and mucus. The
mucus covers the nerve endings of the olfactory nerves that are buried in the
mucous membrane. Because the odor cannot reach the nerve endings, they
cannot detect odor.
Let’s Try This (pages 25–26)
1. Answers may vary. The surface of the table may be smooth or rough,
warm or cold.
2. Answers should be similar to this: Yes. I can feel something wet and
rough at the same time. I can feel the temperature and pressure at the
same time because sensory nerves are scattered all throughout my skin.
3. I was able to identify the objects by feeling them. My familiarity with
their features (texture, edges) helped me identify them.
53
Let’s See What You Have Learned (pages 29–30)
1. epidermis 6. tongue 11. Cilia
2. Olfaction 7. septum 12. skin
3. Saliva 8. Tactile 13. Taste buds
4. nasal cavity 9. chemosensory 14. dermis
5. Receptors 10. Sweet 15. Bitter
D. Lesson 3
Let’s Try This (page 32)
1. Conjunctivitis is the inflammation of the mucous membrane that lines
the inner portion of the eyelid. It also irritates the conjunctiva. It
causes reddening of the eye and is commonly known as sore eyes.
2. Tony said he might have contracted conjunctivitis from the market. He
rubbed his eyes without washing his hands.
3. Conjunctivitis can be prevented by always keeping the hands clean. You
should avoid rubbing your eyes. As much as possible you should also
avoid going to crowded places.
Let’s Review (pages 34–35)
1. My brother or sister must not rub the eye infected with conjunctivitis.
He/She must avoid touching things other than his/her belongings.
Conjunctivitis can easily spread because it is a bacterial infection. If
any other member of the family touches something that was touched
by the person who has conjunctivitis, the former can also get the
disease, especially if he/she touches his/her eyes with hands unwashed.
Thus, the rest of us should avoid touching my infected brother’s/
sister’s things.
N A S A L C A V I T Y R S T R
T S D F D T S D C X Z X A E U
A D J K E I O K E R G H C V B
C F H E E C V B I I J E H D N
T G W L J K P O I N P P J E O
I S D U B E T S A T T I U R I
L M N J K L O P O R F D I S T
E Y T E A S D R R I G E P Z C
W M U T P E S D F B H R O D A
S H J O T R F A D E R M I S F
A I U N Y F I P L N M I L A L
I O P G Y U I O G I L S K S O
L K L U P L K J H B V K J D I
I M R E T T I B N N N A M F H
C H E M O S E N S O R Y S G B
54
2. Lina should not prick the sty in her eye. An infection may develop if
she does so. A sty will burst on its own. She should be patient enough
because it will disappear after a few days.
Let’s Review (page 38)
1. Labyrinthitis
2. Otitis media
3. Labyrinthitis
4. Otitis media
5. Otitis externa
Let’s Try This (page 41)
1. Some of the disorders that can affect the sense of smell are:
♦ Hyposmia or a decrease in sensitivity to smells
♦ Anosmia or a complete absence of smell
These two disorders can result from common colds and
nosebleeds. Common colds and nosebleeds, if not taken care of
properly, can damage the sensitive nerve endings in your nose.
This can result to a loss of smell.
2. Smell disorders can be prevented if you take proper care of your
nose. You must avoid damaging the inner portion of your nose. This
can be done by:
♦ Covering your nose when you are in industrial areas like
construction sites. Dust particles and chemical substances can
enter your nose and damage it.
♦ Avoid inserting objects, including your fingers, inside your nose.
You might damage the mucous membrane lining your nasal cavity.
Let’s Review (page 46)
Causes Symptoms
1. Boils are caused by
staphylococcus bacteria.
These infect the hair roots
and sweat glands.
2. Carbuncle is caused by
Staphylococcus aureus
bacteria.
3. Scabies are caused by an
itch mite called sarcoptes
scabiei.
1. Boils are painful lumps
that can be found in the
armpit, neck, groin, thigh
and at the back of the
knee.
2. Inflammation of the skin
similar to a boil
3. Itchiness on different par
of the skin
55
Let’s See What You Have Learned (page 47)
E. What Have You Learned? (pages 49–50)
A. 1. The eye functions like a camera. It lets light rays enter through
an opening called the pupil. The lens on top of the iris focuses the
light rays on the retina. Inside the retina are light-sensitive cells
(rods that detect black and white colors and are sensitive to dim
light, and cones that detect other colors and are sensitive to bright
light). These light-sensitive cells transform the light rays to
electrical signals, which pass along the optic nerve to the brain.
The brain decodes the messages, thus, enabling us to recognize the
objects that we see.
Diseases Sense Organ Causes/Symptom
1. Conjunctivitis Eye - redness in the in
eyelid and sclera
- excessive wateri
the eyes
- yellowish-green
discharge
- itchiness in the e
2. Otitis Media Ear - caused by a buil
of fluid in the mid
ear
- severe earache
- decrease hearing
- pus
3. Dysguesia Tongue - caused by smok
and radiation
- distortion of taste
- burns on the ton
4. Hyposmia/Anosmia Nose - caused by dama
the nose
- decrease in abili
smell
- complete absenc
smell
- colds
- nasal infections
5. Eczema Skin - dry inflammation
the skin
56
2. The outer part of the ear, the auricle, collects sounds from the
surroundings. Sounds pass through the external auditory canal and
strike the eardrum. Then the eardrum produces vibrations that will
make the other parts of the ear vibrate. When this happens, the
stirrup vibrates and the sounds travel to the inner ear. The fluid
within the cochlea tickles the tiny hairs or nerve endings of the
organ of corti. The organ of corti transforms the vibrations to
nerve impulses that the brain interprets as sounds.
3. Small chemical particles from the surroundings enter the nose
through the air we breathe. Inside the nose is a hollow portion
called the nasal cavity. The cavity is covered by a thin wet tissue
called the mucous membrane. Nerve endings that detect odors are
buried in the mucous membrane. When the particles touch the
nerve endings, they identify the odors of these substances. They
then transport messages to the brain, which interprets these as
smells.
4. When we eat, the food is dissolved by our saliva. The flavor then
spreads all over the tongue. On the surface of the tongue are
small bundles of nerve receptors called taste buds. These detect
the taste of the food we eat. The nerve receptors then send the
message to the brain, which interprets it as either a sweet, sour,
bitter or salty taste.
5. Our skin is very sensitive to touch, pressure, temperature, pleasure
and pain. This is because beneath the skin is an intricate network of
nerve endings that send messages to the brain.
B. 1. You should not rub your eye because you might irritate it,
especially if your hands are dirty. You may bring bacteria into your
eye that may cause an infection. The eye is a very sensitive organ.
2. You should keep your ear dry because fluid in your ear may cause
an infection. If the inside portion of your ear is moist, bacteria
may live there. Also, fluid inside the ear may block the air passage.
When this happens, you may suffer from a decrease, or worse, loss
of hearing.
3. You should avoid being exposed to toxic chemicals because these
can irritate your nose and skin. When toxic chemicals enter your
nose, they damage the sensitive nerve endings that detect
odor. Also, if toxic chemicals come in contact with your skin, you
could develop skin allergies and irritations.
57
4. You should avoid smoking because it damages the sensitive nerve
endings in your nose and tongue. You could damage your taste
buds. This may result to a diminished sense of taste and smell, or
worse, the complete loss of them.
5. You should always keep your body clean to protect yourself from
disease-causing germs and bacteria. This is one way of protecting
your skin from allergies and diseases.
Glossary
Abscess A swollen part of the body in which a thick yellowish liquid (pus or
nana) has collected
Ageusia Reduction or loss of taste
Anesthetic Substance that makes a person or animal unable to feel pain
Anosmia Complete loss of smell
Atopic dermatitis Skin disease popularly known as eczema; itchy, dry
inflammation of the skin
Auditory ossicles Smallest bones of your body—composed of the hammer,
anvil and stirrup
Auricle The outer part of your ear
Bacterial infections Infections caused by bacteria
Blood vessels Tubes through which blood flows in the body
Cartilage A tough flexible tissue attached to the bone
Chemosensory organs Organs that are sensitive to chemicals
Choroid Middle layer of the wall of your eyeball
Cilia Fine hairs inside the nose that trap or filter dust and dirt
Cochlea Coiled structure inside the ear; converts sound waves to impulses
Conjunctiva A thin layer of transparent tissue that covers the sclera
Conjunctivitis Eye infection; commonly known as sore eyes or pinkeye
Cornea Protects the lens of the eye
Dermis Inner layer of the skin; made up of blood vessels and nerve endings
Dysgeusia Distortion of taste
Eardrum Thin tissue that is stretched along the opening of the external auditory
canal
Epidermis Outer layer of the skin
External auditory canal Passage through which sounds travel
Gustatory cells Chemical-sensitive cells that detect taste
58
Hyposmia Decrease in sensitivity to smell
Impurities Dust and dirt
Inflammation A condition in which a part of the body is red, swollen and sore
because of infection
Iris Colored part of the eye which protects it
Labyrinthitis Inflammation of the semicircular canals in the inner ear
Lens Transparent part of the eye behind the pupil; focuses light on the retina
Melanin Colored substance in the iris; absorbs strong light that might shock the
eye
Membrane A thin tissue that connects, covers or lines the sensitive parts inside
the body
Mucous membrane Wet and thin layer of tissue
Mucus Sticky liquid inside the nose produced by the mucous membranes
Nasal Cavity Inner and hollow portion of the nose
Nostrils Two holes or openings at the bottom of the nose where air passes
Olfaction Another term for smell
Olfactory cells Chemical-sensitive cells that detect odor
Optic nerve Passage through which electrical signals pass from the retina to the
brain
Organ of corti Tiny hairs along the cochlea
Otitis Inflammation of the ear
Otitis externa More commonly known as ‘swimmer’s ear’; infection of the ear
canal
Otitis media Inflammation of the middle ear
Polyps Any of several types of abnormal growth in the nose, e.g. pimples,
lumps, boils, ulcers and abscesses
Pupil Center of the eye through which light enters
Receptor Receives stimuli and detects them
Retina Innermost layer of the eye where light-sensitive cells are located
Saliva Sticky fluid in the mouth that dissolves food and spreads flavor
throughout the tongue
Sclera White part of the eye
Semicircular canals Tubes that control balance; sensitive to changes in
movement and direction
Sensation Awareness due to the stimulation of a sense organ
Septum Wall that divides the nasal cavity that forms the nostrils
59
Sty A small abscess of the tissue in the eyelids near the root of an eyelash
Tactile Involving the sense of touch
Taste buds Small bundles of sensory cells that perceive taste
Tear glands Glands that produce tears
Transparent See-through; allows light to pass through so that objects behind can
be clearly seen
References
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