What Is This Module About?
Imagine yourself building a house. What’s the first thing you would do? What are
the first structures you would put up? You would probably set up the supporting posts
first, right? This is because you need to form a framework for that house first. Other
parts that you will add would probably just adapt to the form of the basic structures
you have made. Now, what will happen if these posts would weaken? Your house would
most likely crumble to the ground!
The human body is like the house that you built. It needs a framework, the
supporting structures that maintain the shape of the body and make it function well. In
your body, the framework is provided by the skeletal system. It is a system made up of
bones that give strong structural support and shape to the body.
In this module, you will learn about the skeletal system. You will know what its
parts are and how these parts operate. You will also find out some injuries and
diseases that can harm the skeletal system and how you can best take care of it.
There are four lessons in this module. These are:
Lesson 1 — The Skeletal System
Lesson 2 — The Structure of the Skeletal System
Lesson 3 — The Structure of a Bone
Lesson 4 — Common Injuries and Diseases of the Skeletal System
What Will You Learn From This Module?
After studying this module, you should be able to:
♦ describe the structure and functions of the human skeletal system;
♦ state how the skeletal system works;
♦ identify some injuries and diseases associated with the human skeletal
♦ demonstrate first aid treatment for injury to the skeletal system; and
♦ cite ways to best take care of the skeletal system.
Let’s See What You Already Know
To find out what you already know about the topics to be discussed in this
module, take the following test. Write your answers on the lines.
Enumerate five functions of the skeletal system.
1. _
2. _
3. _
4. _
5. _
What makes up the skeletal system?
6. _
Describe how the skeletal system works during movement.
7. _
Give three injuries or diseases associated with the skeletal system.
8. _
9. _
10. _
Well, how was it? Do you think you fared well? Compare your answers with those
in the Answer Key on page 33.
If all your answers are correct, very good! This shows that you already know
much about the topics in this module. You may still study the module to review what
you already know. Who knows, you might learn some more new things.
If you got a low score, don’t feel bad. This module is for you and it will help you
to understand important concepts that you can apply in your daily life. If you study this
module carefully, you would 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.
The Skeletal System
Most animals need a hard structure in their bodies to maintain shape and provide
support and protection. Some, such as squids and insects, have exoskeletons or hard
supporting structures found outside the body. However, in higher animals like
mammals, the hard supporting structures are found inside the body. These structures
are called endoskeletons or internal skeletons. Human beings have skeletons made up
of bones. Bones are specialized hard structures that form the basic framework and
supporting structure of the body.
In this lesson, you will study the components of the skeletal system. You will
know more about the arrangement and functions of bones. The skeletal system is a
very important part of your body. Are you ready to study it? The lesson is not as hard
as your bones. In fact, you are going to learn a lot of new and exciting things in this
Let’s Try This
Do you know where to find the bones in your body? Try feeling the hard
structures under your skin. Can you feel how hard they are? Hold your head. How does
it feel? The stone-hard structures that you felt are your bones. Do you think that
hardness is important in maintaining the functions of your body?
Let’s Learn
The skeletal system is composed of bones arranged in a way to provide the best
possible support to the organs of the body and to enable you to do a lot of things.
How many bones do you think you have? Make a guess. Is it about twenty? A
hundred? It may surprise you to know that there are 206 bones in the body of an adult.
All these bones are arranged in a special way to make your body function well.
To better illustrate the functions of the skeletal system in the human body,
imagine your body as a house. If the supporting structures of that house are removed it
cannot stand anymore.
Much like the framework of the house, the skeletal system is necessary to
maintain the shape of the body. Without it, you cannot stand erect or maintain an
upright position. The bones in your back and the rest of your body support your weight
to enable you to do things.
The skeletal system also supports the weight
of your body.
The skeletal system maintains the shape of
the body.
Aside from giving support to and providing the framework of your body, the
skeletal system also does a lot of other things.
For example, you are walking in a crowded street when somebody punches you in
the chest.
You feel pain from being hit. Nevertheless, your heart and lungs are unhurt,
unless the force is too great. The hard structure of the skeletal system shielded your
internal organs from the blow.
The bones also serve as attachments for muscles. Human beings move because of
the contraction of these muscles. When the muscles contract or shorten, the bones
they are attached to are also pulled by the action. This causes movement to occur.
Although muscles can move on their own, big body movements are not possible
without the skeletal system. The bones have to move in order for the whole body to
Let’s Think About This
Can you think of three examples of movement that your body can make? How do
you think each of these movements is achieved?
Your body is able to move because muscles are attached to bones. Muscles are
made up of tissue fibers that are able to contract. You can feel your muscles contract
whenever you flex your arms or lift heavy objects. Contracting muscles bulge. Flex
your arms now. Can you feel your muscles contracting?
Muscles are attached to bones on at least two points by dense fibrous structures
called tendons. When muscles contract, bones are moved and brought closer to each
other. This series of muscle contractions causes your body to move.
When muscles contract, bones are brought
closer to each other.
Muscles are attached to bones on at least two
Study the series of movements below. These movements are caused by the
orderly contractions of muscles, one after the other.
The skeletal system is made up of bones that are very hard. Bones are hard
because they contain calcium. Calcium is a mineral that gets deposited in our bones
and teeth to make them tough and sturdy. Aside from providing bones with strength,
calcium also has an important role in other bodily functions. It is an important
requirement for impulse transmission in the nervous system and the movement of the
heart muscle. Hence, because bones store calcium, the skeletal system has a role in
regulating the calcium supply of the body.
Another set of muscles contract while the
previous contracting muscles relax. These
series of contractions cause the body to
Biceps relax
Triceps contract
Calcium is also needed for the proper
functioning of the nervous system and the
Bones are hard because they contain
calcium. 99% of the body’s stored calcium is
found inside the bones.
Biceps contract
Triceps relax
When your arm muscles flex, the bones in
your arms are brought closer to each other.
Lastly, the bones of the skeletal system contain bone marrow, which is important
in the production of blood. It is found in the middle portion of long bones. Hence, the
skeletal system also has an important role in the production of blood through the bone
Let’s Think About This
Imagine waking up one day and discovering that you do not have a single bone in
your body. Your entire skeletal system is gone! What would you do? Imagine how you
would look. What things would you not be able to do? How will you move?
Do you now realize how important the skeletal system is?
Let’s See What You Have Learned
Write True before each correct statement and False before each incorrect
_ 1. The human skeletal system is found inside the body.
_ 2. Bones make up the skeletal system.
_ 3. Bones are hard because of the mineral phosphorus.
_ 4. Teeth and bones are similar in mineral content.
_ 5. The muscular system makes the body move with the help of the bones
through a series of contractions.
_ 6. The skeletal system protects vital organs like the heart and lungs.
_ 7. The skeleton acts as the framework of the human body.
Bones contain bone marrow, the site of production of blood cells that supply oxygen and nutrients to the
_ 8. We could stand upright even without the skeletal system.
_ 9. The skeletal system is valuable only because of its strength.
_10. Bone marrow is important for blood production.
After you have finished, compare your answers with those in the Answer Key on
pages 33 and 34. If your score is 6 or higher, congratulations! You are learning well.
Review some parts you missed to refresh your memory. You may proceed to the next
lesson after going through the items you missed.
If you got 5 or below, don’t be discouraged. You just need more time and effort.
Go back to the parts you missed and study them again. After reviewing this lesson,
you may proceed to Lesson 2.
The Structure of the Skeletal System
In the previous lesson, you learned the many important functions of the human
skeletal system. It is a well-organized system of bones that generally functions as the
framework of the body. Aside from serving as an attachment for muscles and as the
site of blood production, it is also an important storage site for calcium. You might
have seen advertisements saying that calcium makes your bones strong. It is indeed
true. Your bones need to be strong to function well and to keep your body healthy. But
how does the skeletal system accomplish the many amazing things it does? To better
understand this, it is important to learn the structure and arrangement of the skeletal
system in your body.
In this lesson, you will study the arrangement of the bones that comprise your
skeletal system. Are you ready to learn more?
Let’s Think About This
From the previous lesson, do you remember how many bones there are in the
body? If you cannot remember exactly, you can try to feel your bones and estimate
how many you have. While feeling your bones, where do you think you can find the
longest bone? Can you guess where your smallest bone is located? You’ll be surprised
that you might have taken your bones for granted! Remember, your bones give shape
to your body and help it function well.
Let’s Learn
In an adult, the skeletal system is made up of 206 bones arranged in the best
possible way to provide you with a lot of strength and mobility. Because of this
special arrangement, it might seem that your skeletal system is made up of one
continuous bone when it is actually made up of a lot of bones. It may also surprise you
to learn that there are about 220 bones in a newborn child. Some of these bones fuse
together as the child grows older. Hence, adults have only 206 bones!
Have you seen a skeleton before? It might look scary but keep in mind that your
own skeleton is important in making your body stand straight and move. Study the
structure of the skeletal system on the next page. Some of the more important bones
are identified.
From the drawing, what did you notice about the skeletal system? Look at the
figure one more time and write down your observations about the skeletal system in
the blanks below.
1. _
2. _
3. _
If you answered that the skeletal system is made up of many separate bones, you
are correct. In fact, as previously stated, there are 206 bones in the adult skeletal
Also, if you wrote that not all bones appear similar, that’s very good! The bones
are indeed of varying shapes and sizes. Each one is so designed to perform a specific
function. Some of these bones will be discussed later.
If you noticed that the skeletal system is symmetrical, well done! Symmetry
means having similar parts on the left and right sides of the body. This symmetry is
visible in the way your body looks from the outside. This is because the skeletal
system is symmetrical too!
Phalanges (fingers)
Phalanges (toes)
Look at the figures below. They show how symmetry is maintained both inside
and outside the body.
Let’s Try This
Pause for a while and look carefully at the skeletal system again on page 11.
Which parts of the body do you think are composed of longer bones? Which parts are
composed of smaller bones? Why are there larger bones? Why are the smaller bones
found in those particular parts of the body?
The skeletal system is made up of
bones that are arranged in a unique
structure. Bones are held together by
fibrous structures called ligaments.
Ligaments maintain the arrangement of
the bones. Study the skeletal system on
the left.
Larger bones like the skull and
bones of the pelvis are found in the
central parts of your body. Smaller
bones like the digits of your hands and
the bones of your toes are farther away
from the center of the body.
The bones in the central or middle
portions of the body are for making gross motor movements. These are big and
powerful movements that you make when you jump, run, or somersault. The more
peripheral or sideward parts have smaller bones. These bones are for fine motor
movements. Examples of these fine movements are writing and stitching. The above
examples give you an idea of how the skeletal system’s arrangement makes you move
and perform better.
Can you think of other examples of fine motor movements? How about gross
motor movements? The gross motor movements develop earlier than fine motor
movements. This pattern of development is called proximodistal growth, which
means growth that proceeds from the center of the body to the extremities. Because
of this, you would expect adults to have finer motor movements than babies.
Let’s Review
In the spaces before each statement, write True if the statement is correct and
False if the statement is incorrect.
_ 1. There are 208 bones in the human body.
_ 2. The skeleton is the structural arrangement of bones in the human
_ 3. All bones are of the same size.
_ 4. All bones are of the same shape.
_ 5. Bones give shape to the body.
_ 6. Painting a picture is a fine motor movement.
_ 7. Writing is a gross motor movement.
_ 8. The bones in the central part of the body are generally larger.
_ 9. Proximodistal pattern of bone development means bone
development starts from the center and progresses to the extremities
of the body.
_ 10. The bone of the head is called the skull.
Compare your answers with those in the Answer Key on page 34. If your score is
6 or higher, very good! You already know your skeletal system better. Review some
parts you missed to refresh your memory. You may proceed to the next part of this
lesson after you finished going through the items that you missed.
If your score is 5 or below, it’s okay. But you may need to go back and study the
items you missed. After doing so, you may proceed to the next section.
Recognizable bones in your body
In this part of Lesson 2, you are going to study some of the more recognizable
bones in your body. All bones are important because each one works with another to
create a functioning whole. Studying more about these bones will make you know
more about the skeletal system. Go over each bone discussed and try to feel that bone
in your body while reading how it is described.
The skull is the bone of your head. It
protects the brain and other sensory
organs from harm. It is one of the
strongest bones in your body. The skull is
not a single bone; it is composed of 26
bones fused together to protect the
structure of the head.
The vertebrae are small but thick
bones that comprise the spine or the
backbone. The structure of the vertebrae
allows a greater range of motion to the
trunk of the body. The vertebrae protect
the spinal cord.
Twelve pairs of ribs are attached to
the sternum or breastplate to form the
ribcage. The ribcage protects the vital
organs of the body such as the heart,
lungs, and liver.
The pelvis is made up of several thick
and wide bones that protect the organs of
the reproductive and urinary systems. The
structure of the pelvis greatly affects the
outcome of a pregnancy. Wider pelvises in
women allow the passage of the baby at
The humerus is the bone of the upper
arm. The humerus makes arm movements
The femur is the bone of the upper leg.
It is the longest bone in the body and it
greatly contributes to your height.
symphysis pelvic brim
The phalanges are the bones of the
hands and fingers. There are approximately
20 bones in each hand. The smaller bones
of the hands and fingers allow finer motor
movements to be performed.
The ossicles are a group of bones
found inside the middle ear. There are three
ossicles. These are the hammer, anvil, and
stirrup. The ossicles are the smallest bones
in the body that vibrate to amplify sound to
allow better hearing.
anvil stirrup
Let’s See What You Have Learned
From the drawing of the human skeletal system on page 17, identify the location
of the following structures.
Skull Humerus Vertebrae
Ribcage Femur Pelvis
Sternum Phalanges
Let’s Remember
♦ Bones are arranged in a very organized manner that provides the body
support, protection, and the easiest movements possible.
♦ The adult human skeleton is made up of 206 bones, some of which are made
up of smaller bones fused together.
♦ Bones are of varying sizes and shapes.
♦ The human body is symmetrical because of the skeletal system.
♦ Bones are attached to each other by ligaments.
♦ Bones in the center of the body are capable of gross motor movements.
Bones in the periphery are involved in producing fine motor movements.
♦ Each bone has a name and a distinct location. The bones discussed in the
lesson are the skull, vertebrae, ribs, pelvis, humerus, femur, phalanges, and
The Human Skeletal System
Compare your answers with those in the Answer Key on page 34. If your score is
6 or higher, congratulations! You are now able to identify the more important bones of
the body. Review the items you missed to refresh your memory. Afterwards, you may
proceed to the next lesson.
If your score is 5 or below, you might need to study the lesson again. After doing
so, you may proceed to the next lesson.
The Structure of a Bone
In the previous lesson, you learned about the structure and organization of the
skeletal system. You also studied more closely some of the bones found in the body.
To help you better understand what makes bones function so well, this lesson will
introduce you to the characteristics and properties of individual bones. A typical bone
will be analyzed to show how each bone works.
Think of this lesson as you look closer at a piece of bone. Knowing how that
single bone works will give you an idea of how the entire skeletal system functions.
Are you ready?
Let’s Think About This
Have you ever seen a human bone? Even if you haven’t seen one yet, chances are
you have already seen bones of other animals. Examples would be chicken or beef
bones found in some of your favorite dishes. Do you remember what these dishes are?
How do they look? Close your eyes and imagine what animal bones look like.
Let’s Try This
After imagining, maybe you can go much further by actually getting an animal’s
bone. It may be from a chicken or any other animal. If you already have one, touch that
bone. How does it feel? Have you ever wondered how this small bone works?
Let’s Learn
A bone is a special form of connective tissue made up of a special protein
material called collagen — which is saturated with calcium. There are two structural
types of bones — compact and spongy bones. Compact bone is solid and dense, and
it forms the outer shell of the bone. Spongy bone is less dense than compact bone
and is made up of thin threads of bones. All bones are made up of a combination of
these two. Study the structure of the cross section or cut specimen of a bone in the
drawing on the next page. Notice how the collagen acts like a scaffolding or a
framework in which calcium is deposited.
Calcium is a stone-like mineral that makes your bones strong. It is the reason
why bones appear white on X rays. It is also the same material that makes teeth hard
enough to chew food. Calcium allows bones to respond to the stress and strain you put
on them. It is found in foods like cheese and milk.
When calcium enters your body,
99% of it goes to your bones for
storage. As previously stated in
Lesson 1, calcium is also important
for the other functions of the body
especially in the nerves and muscles.
When these organs need calcium, they
absorb the calcium deposits inside the
bones through a special process called
bone resorption. In this process,
calcium is released through the
destruction of actual packets of bony
tissue. Hence, bones are continuously
being built up and destroyed.
Contrary to popular belief, bones
are not static or unchanging. Bones
are living tissues that are continuously
being built up and absorbed,
constructed and destroyed. Hence, it
is important for you to get a lot of
calcium in your diet to keep your
bones strong. Proteins are also
needed to maintain normal bone structure and function. Soybeans, meat, fish, and
vegetables are important sources of protein.
Bones are vascularized. This means that they have a rich blood supply. In adults,
human blood flows through the bones at an average of 200 to 400 milliliters (mL) per
Most bones start out as cartilage. Cartilage is a whitish fibrous material that is
both tough and strong but contains a lot of water. You may have seen cartilage in the
breast of a chicken. As you grow older, the cartilage ossifies. Ossification is the
process of hardening due to the deposition of minerals, especially calcium. Adults
have stronger bones than children because their bones are already much more
ossified. Most long bones in the body have bony centers and cartilage in the ends. This
type of cartilage is called epiphysis. The epiphyses are the areas where bone growth
happens. The elongation of your bones allows you to become taller. The drawing on
page 19 the left shows the epiphyses of a long bone like the femur.
Note also that inside the long bones, you can find the bone marrow. The centers
of these bones are hollow, where cells that form blood are found. Hence, this
illustrates how important bones are in the process of blood production.
Let’s See What You Have Learned
Write in the blank the letter of the phrase in Column B that matches the term in
Column A.
1. calcium a. process of calcium deposition
2. 200 to 400 mL b. having a rich blood supply
3. epiphyses c. sites of bone growth
4. collagen d. whitish fibrous material
5. bone marrow e. mineral stored in bones
6. ossification f. nutrient found in meat and fish
7. protein g. important for blood production
8. cartilage h. protein material that makes up a
9. vascularized i. average amount of blood that
flows through the bones per minute
10. bone resorption j. bone destruction
Compare your answers with those in the Answer Key on page 35. If your score is
6 or higher, you did great! You have learned a lot about the structure and functions of a
bone. Review the items that you missed, then proceed to the next lesson.
If your score is 5 or below, that means you need to study this lesson again.
Afterward, you may proceed to the next lesson.
Let’s Remember
♦ Bones are living tissues. They are continuously being formed and absorbed
in a process called bone resorption.
♦ Bones are made up of collagen fibers saturated with calcium.
♦ Calcium is stored in bones and is important for the nerves and muscles to
function well.
♦ Proteins are also important to bone structure and function.
♦ Bones are well vascularized or rich in blood supply.
♦ Bone marrow is found in the hollow center of long bones. The bone marrow
is made up of cells that produce blood.
♦ Bones start out as cartilage and become hard through the process of
ossification or the deposition of minerals, especially calcium.
♦ Ossification centers, which are important for the growth and elongation of
the long bones, are found in the epiphyses.
Common Injuries and Diseases of the
Skeletal System
Have you ever seen somebody with a plaster cast around his arm? What do you
think happened? Have you ever had a bad fall? What were the injuries you sustained?
Was your skeletal system affected? If you have seen somebody with a plaster cast on
his leg or arm, chances are, he has a fracture. A fracture is a break in a bone.
In the previous lessons, you learned about the structure and functions of the
skeletal system. You already have an idea of the great responsibility of the bones in
protecting you and allowing you to do your work. Although the skeletal system is the
strongest structure found in your body, it is still prone to a lot of injuries and
diseases. In this lesson, you will learn about these injuries and other conditions that
can affect your skeletal system. You will also know how to best take care of your
skeletal system and keep it healthy and functioning well.
Let’s Try This
To experience how difficult life is if the skeletal system is injured, do this
exercise: Wrap the arm that you use for writing with enough layers of cloth to keep it
from moving. After making a “cloth cast,” put a sling around your arm following the
illustration below. Make sure that you do not wrap the cast too tightly to avoid a
decrease in blood supply to your “affected” arm. Continue doing your daily routine
with the cast on for about 6 hours. Try taking a bath and eating with your cast on. Then
write down your observations by the end of the period while the cast is still on. What
did you learn from this exercise? Were you able to appreciate the bones of your body
How to make a sling for the cloth cast
Although the skeletal system is strong, it is still prone to diseases. There are a lot
of injuries and disorders that can affect this system. The following are just some of
them. While reading about each, think of anybody you know who might have a similar
injury or bone disorder. Visualize that person as you learn more about the condition.
A fracture is a broken bone. Some fractures are closed, some are open. Closed
fractures are broken bones with unbroken skin. Open fractures have broken skin,
usually with the bone coming out of the site of injury. Open fractures are worse
because they are more prone to infection and indicate a larger amount of damage to
the bone. Fractures are most often caused by traumatic accidents and bad falls.
The figures below show several types of fractures of the humerus — the bone of
the upper arm.
First Aid for Suspected Bone Injuries
(What to do when there is a fracture)
1. When a person suffers a traumatic accident or a bad fall, it is best to assume
that a bone is broken.
2. When a fracture is present, there is usually swelling of the fractured area and
the patient is unable to move the affected body part. Fractures are most often
painful and the patient might cry in agony.
3. When the affected area is an extremity like a leg or an arm, check the area. If
there is an open wound (usually with a protruding bone part) call for help
immediately. You may ask someone else to call for help while you attend to
the patient.
Simple Compound Comminuted Greenstick
4. Control bleeding by putting a direct, steady pressure on the area using a
cloth or any dampening material. Never attempt to put back the bone to its
original position by pushing or pulling it. Other structures like the muscles,
nerves, and blood vessels might be damaged. This might cause more harm
than good.
5. The most important thing to do for any type of fracture is to immobilize the
affected area. Immobilization means limiting movement and hence
avoiding further damage.
Immobilization can be achieved through splinting. You can use any hard
and steady material available such as a piece of flat wood, folded paper,
carton, or cloth. The diagram below shows how a basic splint is constructed.
If a splint is not available, you can immobilize the affected body part by
creating a sling. A sling is a large piece of cloth used to create temporary
immobility, usually in the arms.
6. While the patient is immobilized, call for help. Stay with the patient. Make
him/her as comfortable as possible with the least amount of movement.
7. If a closed fracture is noted, the same procedure is followed. Again,
remember the important principles in management of fractures, namely
immobilization and immediate referral for medical attention.
8. Even if the affected area is movable and there is very minimal pain, it is still
advisable to seek medical attention. Some fractures are small in scale and
are only detected through X rays. It is best not to rule out any body injury in
traumatic events.
9. The principle of immobilization is more important when a neck fracture is
suspected. This is most common after a bad fall from a high position. Never
attempt to move the patient. Neck fractures are potentially life threatening.
Seek medical attention immediately. While waiting for help, you can ensure
immobilization by doing a makeshift cervical collar using two bottles or any
other similar hard objects and placing them on each side of the patient’s
Disorders of the Spine/Backbone
You are walking to school one day when you notice somebody who has an
unusually arched back. Because of this condition, he finds it very difficult to walk or
move fast. What do you think happened to the bones of this person’s back?
A hunchback is someone who suffers from kyphosis, a condition caused by too
much outward curvature of the vertebral bones. This makes it difficult for the person
to move fast. Too much sideward movement of the same bones would also lead to a
deformity called scoliosis. Both kyphosis and scoliosis result from unknown causes.
They usually develop during adolescence. Traumatic injuries may also cause these
conditions. Treatment involves the use of back braces, physical therapy or surgery.
To check if somebody has scoliosis, ask that person to bend and touch his/her
toes with both hands while standing. Observe the person from behind. He/She might
have scoliosis if the slope of his/her back is not smooth as shown below.
Rickets is caused by vitamin D deficiency, especially in children. Vitamin D is
important in the deposition of calcium inside the matrix or inner structure of bones to
provide bone strength. Persons with rickets have very weak bones because of low
calcium content. A lot of them are bow-legged and weak. They can only do very
limited movements. Most of the time, too much damage has been done to the bones
that they are already impossible to cure.
Jose and Rosa are very small people. They were born that way. Their bodies look
normal in size but their arms and legs are very short. What do you think are the
difficulties Jose and Rosa have to face every day?
Dwarfism has two types. A true dwarf is called a midget. Midgets have
proportional body structures but are very small. They are usually 3 feet or below in
height. Achondroplasia, which Jose and Rosa have, is the more common type of
dwarfism. Achondroplastic dwarves have normal-sized bodies but they have very
short arms and legs. Both conditions are genetic and inborn, and they have no known
Lolo Antonio is 75 years old. He often complains of very painful joints. He
suffers constant pain in his hips, knees, and hands. Sometimes these parts swell,
making the pain worse. Because of this, he avoids too much physical activity and just
stays at home.
Osteoarthritis literally means inflammation of the joints. Osteoarthritis is more
common among the elderly. Joints are inflamed because of the abrasion of the joint
linings due to old age or constant physical exertions. People with arthritis usually
complain of very painful and sometimes swollen joints. Arthritis can also occur
among the young. Painkillers are the first line of treatment.
A condition very common in old women is osteoporosis. It is the loss of bone
minerals that lead to brittle, easily fractured bones. This condition is very common
among post-menopausal women due to lack of estrogen, a hormone that inhibits bone
resorption. Patients are treated with calcium supplementation, hormone replacement,
and physical therapy.
A sprain results from the overstretching of the ligaments that connect bones.
Ligaments are stretched too much when an extreme motion is abruptly performed like
reaching too far for an object or twisting an ankle. To avoid sprains, stretching
exercises should be performed before a stressful activity such as dancing or playing
basketball. Like fractures, sprains are healed through immobilization.
You have just studied some of the most common injuries and disorders of the
skeletal system. Of course, there are other conditions that can possibly affect your
bones. Hence, proper care should always be observed.
Let’s Think About This
Think of some ways you can promote the health of your bones and avoid diseases
of the skeletal system? List down as many as you can on a separate sheet of paper.
Now go back to your list. Are you observing proper care of your skeletal system?
Proper Care of the Skeletal System
Properly arrange furniture and
other equipment around you to avoid
Eat a lot of protein-rich foods such
as soya beans, vegetables, meat, and fish.
Eat a lot of foods rich in calcium
such as milk and dairy products.
Always wear or use protective
gear when a traumatic injury or fall is
likely to happen, such as in
Avoid activities that may cause
traumatic body injuries and bad falls such
as climbing on top of an unstable
Keep floors dry to avoid slipping.
Keep things orderly. Playthings left
on the stairs might cause accidents.
Lift objects properly. Avoid bending
forward when carrying a heavy load.
You have just learned some ways of taking care of the skeletal system. In this
module, you were introduced to the structure and functions of the skeletal system, the
structure and function of a bone, and the injuries and disorders that can affect the
skeletal system. Indeed, the skeletal system is a wonderful structure that serves a very
important role in your life.
Rest regularly. Avoid too much strain
on your bones and joints.
Always seek medical help when a
bone injury is likely to have occurred.
Let’s See What You Have Learned
Identify what is being described by each phrase.
1. broken bone
2–3. two important principles in handling fractures
4. common bone defect in old women
5. also known as a midget
6. hormone that inhibits bone resorption and thus prevents

7. vitamin that can prevent rickets
8. inflammation of the joints
9. two most important food nutrients for the skeletal system
10. large piece of cloth used to immobilize an arm
Check your answers against those in the Answer Key on page 35.
Review the parts you missed in the last lesson of this module. Feel free to go
back to any lesson you may have had difficulty with.
Let’s Remember
♦ Bones, strong as they are, are still prone to injuries and disorders.
♦ Injuries to the bone and its ligaments can cause fractures and sprains.
♦ Bone disorders include kyphosis, scoliosis, rickets, arthritis, and dwarfism.
These can be inborn or due to old age, improper nutrition, infections, or
traumatic injuries.
♦ Taking care of the bones requires proper nutrition, avoiding injuries, seeking
medical help, and maintaining proper hygiene.
You have now reached the end of the module. Congratulations! Did you enjoy
reading it? Did you learn a lot from it?
The following is a summary of its main points to help you remember them better.
What Have You Learned?
Write True if the statement is correct and write False if the statement is

_ 1. The skeletal system is made up of bones.
_ 2. Bones are hard because of the calcium deposited inside.
_ 3. Bones provide the framework of the body.
_ 4. Bones usually start as cartilage.
_ 5. Bone growth occurs in the epiphyses.
_ 6. All bones in the body have the same name.
_ 7. A break in the bone is called a sprain.
_ 8. Broken bones should be moved constantly.
_ 9. A sling is made of wood only.
_ 10. Protein and calcium should be included in your diet to keep your
bones strong.

_ 11. Scoliosis is a backward curvature of the spine.
_ 12. The spine is also called humerus.
_ 13. Injuries can be avoided by wearing protective gear.
_ 14. Running is an example of a gross motor movement.
___ 15. All bones look the same.
After you finish answering the questions, check your answers in the Answer Key
on page 35. If you got 13 or more correct answers, well done! You learned a lot from
this module. Keep it up! Apply what you have learned about the skeletal system to
better take care of your bones. If your score is 12 or below, it’s okay. But you need to
go back to the parts of the module where the answers you missed can be found.
Let’s Sum Up
♦ The skeletal system is a well-organized system of bones that has many
functions. The skeletal system serves as the framework of the body, supports
its weight, maintains its shape, and protects internal organs. Bones also
participate in the storage of calcium needed to maintain the body’s
♦ Bones are arranged in the best possible way to allow movements of the body.
Bones serve as attachments for muscles that contract during movements. A
bone is made up of a collagen matrix or structure laden with minerals,
mostly calcium, that make it strong.
♦ Injuries to the bones such as fractures and sprains are common.
Immobilization or preventing movement is the primary aim in the
management of fractures. Medical help is also very important. Several
disorders affecting the bones are rickets, arthritis, and osteoporosis.
Answer Key
A. Let’s See What You Already Know (page 2)
1. Provides framework to maintain body shape
2. Protects internal organs
3. Acts as surface attachment for muscles that are important for
4. Serves as a storage site for calcium and helps in the metabolism of
5. Supports the body when lifting objects
(Another possible answer: Contains the bone marrow, which is the site of
blood formation)
6. Bones
7. The skeletal system is closely associated with the muscular system.
Bones act as attachments for muscles. When muscles contract the
bones move, thus enabling motion.
8. Fractures
9. Rickets
10. Osteoporosis
(Other possible answers: scoliosis, kyphosis, dwarfism, osteoarthritis,
B. Lesson 1
Let’s See What You Have Learned (pages 8–9)
1. True
2. True
3. False. Bones are hard because of the mineral calcium.
4. True
5. True
6. True
7. True
8. False. Only the bones are strong enough to support the weight and
structure of our body.
9. False. The functions of the skeletal system are not all strength-related,
for example, the blood formation inside the bones.
10. True
C. Lesson 2
Let’s Review (page 13)
1. False. There are 206 bones in the human body.
2. True
3. False. Bones vary in size.
4. False. Bones vary greatly in shape.
5. True
6. True
7. False. Writing is a fine motor movement because it requires the use of
the fingers.
8. True.
9. True
10. True
Let’s See What You Have Learned (pages 16–17)
D. Lesson 3
Let’s See What You Have Learned (page 20)
1. e 6. a
2. i 7. f
3. c 8. d
4. h 9. b
5. g 10. j
E. Lesson 4
Let’s See What You Have Learned (page 31)
1. fracture 6. estrogen
2. immobilization 7. vitamin D
3. medical attention 8. osteoarthritis
4. osteoporosis 9. calcium and protein
5. true dwarf 10. sling
F. What Have You Learned? (page 33)
1. True. Bones make up the human skeleton.
2. True. The mineral calcium makes bones strong.
3. True. Bones also provide support to the body and maintain the body’s
4. True. The cartilage undergoes the process of ossification or bone
5. True. Bone growth occurs in epiphyses of the long bones.
6. False. Each bone has its own name.
7. False. A break in the bone is called a fracture.
8. False. Broken bones should be immobilized to prevent further injury.
9. False. A sling is usually made of a triangular piece of cloth.
10. True. Both are needed for proper bone function.
11. False. Scoliosis is a sideward curvature of the spine.
12. False. The spine is also known as backbone. The humerus is found in the
upper arm.
13. True. Protective gear such as helmets and gloves should be worn when
doing potentially dangerous activities.
14. True. Running is an example of gross motor movement, it involves the
bones of the central part of the body.
15. False. Bones vary in shape and size.
Achondroplasia Genetic bone abnormality manifested by very short arms and
Bone The basic component of the skeletal system.
Bone marrow Site of blood production inside bones.
Bone resorption The process in which calcium found in bones is reabsorbed by
the body.
Calcium Mineral needed for bone strength and hardening.
Cartilage “Soft bone”; the common origin of hard bones.
Collagen Protein matrix of bones.
Dwarfism A condition characterized by shortness, usually 3 feet or below.
Epiphysis Site of bone growth.
Exoskeleton The hard outer covering of some animals.
Femur Bone of the thigh; longest bone in the body.
Fine motor movements Small movements like writing; involve the fingers or
smaller bones.
Fracture A break in the bone.
Gross motor movements Big movements, such as running, involving bigger
Humerus Bone of the upper arm.
Immobilization Limiting or preventing movement to prevent complications in
Kyphosis Hunchback, outward curvature of the spine.
Ligaments Fibrous tissues that connect bones.
Ossicles Bones of the inner ear composed of the hammer, anvil, and stirrup.
Osteoarthritis Inflammation of bone joints common in the elderly.
Osteoporosis Weakening of bones due to calcium loss, especially evident in
older women.
Pelvis Bones of the buttocks and groin.
Phalanges Bones of the fingers or toes.
Proximodistal growth Pattern of bone development starting from the center of
the body to the extremities.
Ribs Bones of the chest protecting the heart and lungs.
Rickets Weakened bones due to vitamin D deficiency.
Scoliosis Abnormal sideward curvature of the spine.
Sprain Overstretched ligaments.
Skeletal system An organ system made up of bones that give structural support
to the body.
Skull Also known as cranium; houses the brain.
Spine Also known as backbone or vertebral column.
Strain Overstretched tendons.
Tendons Fibrous structures that connect muscles to bones.
Vascularized Rich in blood supply.
Campbell, N. Biology. 4th ed. U.S.A.: The Benjamin and Cummings Publishing
Company, Inc., 1988.
Junquiera, LC, J. Carneiro, and R. Kelly .Basic Histology. 6th ed. Appleton and
Lange Prentice Hall, 1989.
Rischer, C. and T. Easton. Focus on Human Biology. 2nd ed. Harper Collins
College Publishers, 1995.
Singer, S. and H. Hilgard. The Biology of People. San Francisco: WH Freeman
and Co., 1978.
Van de Graaff, K. and Stuart I.F. Forx. Concepts of Human Anatomy and
Physiology. 2nd ed. Iowa: WM Brown Publishers, 1985.

1. http://depts.washington.edu/bonebio/
This site includes the following information:
Facts about bones
How to build your bone strength
Bone diseases

This site tackles the skeletal system and its parts. It has an interactive multimedia presentation.

This site includes the following information:
What would happen if humans didn't have bones?
How many bones do humans have?
How do my bones move?

This site offers a virtual body which includes the Skeletal System

An interactive game. Drag the part of Skeletal system to the appropriate location. Gives hints and definition about the part that is on the screen.

This site includes:
The functions of Skeletal System
Different links to the parts of skeletal system, its pictures and functions
Also included in this site is the quiz about the content of the said website

This site includes the overview, tasks, process and pictures of the human skeletal system

This website contains an interactive picture of the skeletal system. By clicking on a part of the skeletal system, it will display its picture and functions.

An interactive game that shows a scattered bones and for you to put them on the right place. By clicking on each part, it will show its name.

An interactive activity about the human skeletal system

This website has links to the different parts of the skeletal system. Each links inlcude the functions and actual pictures of the parts of the skeletal system.

This website shows the different parts of skeletal system by pointing out on the picture where it is and telling its definition and functions.
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Real photographs of the human skeletal system, including a quiz.

A 14-question interactive quiz.

A clickable quiz of the human arm bones.