Download Teachers Guide - Discovery Education

OUR FLEXIBLE FRAME
1 videocassette . . . . . . . . . . . . . . . 23 minutes
©Copyright 1989
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TABLE OF CONTENTS
Introduction ........................................................................ 1
Program Summary.............................................................. 1
Learning Objective............................................................. 4
Review Questions............................................................... 5
Activities............................................................................. 9
Glossary............................................................................ 21
Bibliography..................................................................... 24
Related Videos From Rainbow......................................... 25
Script................................................................................. 12
INTRODUCTION
Where would we be without bones and muscles? Skeletons
may make us think of Halloween, and muscles may bring to
mind body builders; but together the skeletal and muscular
systems give our bodies shape and support, and allow us a
wide range of movement. All our activities — everything we
do that allows us to survive and gives us enjoyment — come
about in large part through the way our muscles and skeletons
are constructed and the ways in which they work together.
The video program Our Flexible Frame: The Skeletal
and Muscular Systems describes these two systems of the
human body and explains how they work, separately and
together. The information is presented at a level appropriate
for middle schoolers, and the program makes liberal use of
animated graphics and real-life examples to convey the facts
and maintain viewer interest.
The video can serve as an introduction to the skeletal and
muscular systems, or it can help reinforce and amplify concepts that students have already studied. This guide provides
suggestions for review questions and for activities that can
enhance students' understanding of the material and extend
the concepts presented in the program.
As the program opens, a woman performs a karate exercise,
demonstrating how the skeletal and muscular systems give
the body shape, stature, mobility and strength. Similarly, the
delicate brushstrokes of a painter show how fine movements
depend on the coordination of muscles and bones. In fact,
everything we do requires the support of bones and muscles.
The program goes on to present some facts about bones: our
bones come in many shapes and sizes, from the long thigh
bones to the tiny bones of the inner ear. In the hand alone,
there are 27 different bones. A baby is born with about 300
bones, but some of these grow together, or fuse, so that an
adult has only 206 bones. A baby's bones are soft and
flexible because they are mostly cartilage. But as the bones
grow, new cartilage is formed and then replaced by hard bone.
This process slows during later childhood, but speeds up
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© MCMLXXXIX Rainbow Educational Video. Inc.
during the teenage growth spurt. By the late teens, most
cartilage has been replaced by hard bone.
An image of bleached bones in the desert illustrates the
way we often think of bones — as brittle, hard, and dead.
Yet, as the program points out, bones are very much alive.
Like all tissues, bones are made of cells. These cells secrete
minerals, calcium and phosphorus, that make the area around
each cell hard. Both calcium and phosphorus are contained
in milk, which is why milk helps build strong bones.
The program goes on to look at the structure of a bone
— specifically, the femur, or thigh bone. This bone's outer
part consists of a tough, hard membrane. Beneath the membrane is a layer of strong, hard bone tissue called compact
bone. Beneath this layer is a cavity that extends through the
center of the femur, making it light in weight. Inside this cavity is
a soft tissue called yellow marrow. At the ends of the femur
there is a different kind of bony tissue, called spongy bone
because it is filled with spaces, like a honeycomb. These
spaces contain another kind of marrow, red marrow.
Next, the video details the four major functions of the
skeletal system. First, our bones support our bodies and give
them shape. Without our skeletons, we would collapse like
masses of jelly. Second, our bones protect our vital organs.
The skull, the vertebrae, and the ribs are cited. Third, the
skeletal system manufactures red blood cells in the red marrow, producing them at the rate of two million cells a second.
Fourth, the skeletal system provides a flexible framework to
which muscles are attached, allowing the body to move. How
bones join together is demonstrated by the bones of the leg:
the femur, or thigh bone, connects at the knee with bones in
the lower leg and with the bone that forms the kneecap. The
bones of the leg are held together by tough, flexible bands
of tissue called ligaments, and the ends of the bones are
cushioned by protective pads of cartilage.
The program goes on to discuss joints. The movements
of a baseball pitcher show how different joints allow for different kinds of motion: hinge joints, with their back-and-forth
movement; the saddle joint, for lateral movement of the
thumb; the pivot joint, which allows the head to turn independent of the body; and ball-and-socket joints, which let us
move our limbs in almost any direction. The fixed joints of
the skull, with their zig-zag seams, are examples of joints
that do not permit movement.
A sequence of a dancing marionette reinforces the idea
that joints are necessary for movement. But, the program
points out, while a puppet has a puppeteer to pull its strings,
human beings rely on muscles for movement. An animated
graphic shows how muscles and tendons in the arm allow
the lower arm to be raised; the examples of a karate kick
and someone hammering a nail show different ways in which
legs, hands, and arms move. A mime demonstrates the range of
facial expressions made possible by muscles in the face and
shows how muscles are working even when we are standing
still. All together, the program points out, there are more
than 650 muscles in the human body, and they make up
nearly half a person's total body weight. Besides skeletal
muscles, there are cardiac muscles that make up the heart,
and smooth muscles that line some of our internal organs.
For example, smooth muscle helps to move food through the
digestive tract, and blood through arteries and veins.
The program differentiates between voluntary and involuntary muscles. Smooth and cardiac muscles are involuntary muscles; we don't consciously control them. Skeletal
muscles are voluntary; we do consciously control them, as
when a painter moves her brush very deliberately. Some
voluntary movements, as in a sport like skiing, may with
practice and repetition become almost second nature.
The program shows that muscles work by contracting and
relaxing, and that many skeletal muscles work in pairs.
Graphics of the biceps and triceps muscles in the upper arms
demonstrate how two muscles work together.
The program also emphasizes that if muscles aren't used,
they will become weak and flabby, because muscle cells,
also known as fibers, decrease in size if they are not active.
Exercise helps muscles become larger and stronger — and
this is true of the heart as well as the skeletal muscles.
The program concludes with a summary of the main points.
LEARNING OBJECTIVES
After viewing the program students should:
1.
Understand the importance of the skeletal and muscular
systems to the human body.
2.
Understand that muscles and bones work together.
3.
Understand how cartilage is replaced by hard bone as
people grow from infancy to adulthood.
4.
Know certain facts about the structure of the human
skeleton; specifically:
— that bones are of greatly varying sizes and shapes
— that babies have about 300 bones, while adults,
due to the fusing together of bones, have 206
— that bones are made up of cells
— that bone cells secrete calcium and phosphorus,
minerals that give bones their hardness
5. Know certain facts about individual bones; specifically:
— that a bone shaft has three layers: an outer membrane, a layer of hard bone, and a cavity containing
yellow marrow
— that the ends of long bones contain spongy bone
tissue filled with spaces containing red marrow
6. Understand four main functions of the skeletal system;
specifically:
— to give the body shape and support
— to protect the body's vital organs
— to produce red blood cells
— to provide a flexible framework that, in conjunction with muscles, allows the body to move
7.
Understand the functions of ligaments and cartilage
pads in joining bones to each other.
8. Recognize and understand different types of joints;
specifically:
— hinge joints, as in the elbow
— saddle joints, as in the thumb
— pivot joints, as in the neck
— ball-and-socket joints, as in the shoulder
9.
Understand how tendons allow muscles to move bones.
10. Know certain facts about muscles; specifically:
— that there are more than 650 different muscles in
the human body
— that muscles make up almost half of our body
weight
11. Recognize and understand the terms: skeletal muscle,
cardiac muscle, and smooth muscle.
12. Know the difference between voluntary muscles and involuntary muscles.
13. Understand that muscles work by contracting and relaxing.
14. Understand how skeletal muscles work together in pairs.
15. Appreciate the role of exercise in maintaining strong
and healthy muscles.
QUESTIONS FOR REVIEW
AND DISCUSSION
1. What are the largest bones of the human skeleton?
[The femurs, or thigh bones, are the largest.]
2. Which bones in the human body are the smallest?
[They are three tiny bones deep inside the ear.]
3. About how many bones does a newborn baby have?
[A newborn has about 300 bones.]
4. About how many bones does an adult have?
[An adult has about 200 bones — 206, to be precise.]
5. Why does an adult have fewer bones than an infant?
[As an infant grows, some bones fuse, or grow together,
resulting in a smaller total number of bones.]
6.
Why are a baby's bones so flexible?
[They are composed mainly of cartilage.]
7. Why is it that the bones of an adult are hard and brittle
compared to those of an infant?
[As bones grow, new cartilage is formed and then replaced by hard bone. This process continues during child.hood and speeds up dramatically during the teenage
years. By adulthood, most cartilage has been replaced
by hard bone.]
8. What are the minerals that make bone hard?
[Calcium and phosphorus, secreted by bone cells, make
the areas around these cells hard.]
9. Describe the structure typical of a large bone, like the
femur.
[The outer part of the bone is a hard, tough membrane.
Under the membrane is a layer of hard bone called compact bone, which gives the bone its strength. Extending
through the center of the shaft is a cavity filled with yellow
marrow. At the ends of the bone is a spongy bone tissue,
which contains honeycomb spaces filled with red marrow.]
10. What are the four important functions of the skeletal
system?
[I) The skeleton gives the body shape and support. 2)
Bones protect vital organs such as the brain, spinal cord,
heart, and lungs. 3) The red marrow produces red blood
cells. 4) The skeletal system works with muscles to allow
movement.]
11. What is the main function of red blood cells?
[They transport oxygen throughout the body.]
12. Why must red blood cells be replenished, and how
does the skeletal system work to ensure an adequate
supply?
[Red blood cells have a life span of only about 125 days;
then they break down and die. Red marrow manufactures
about two million red blood cells per second.]
13. What are ligaments?
[Ligaments are tough, flexible bands of tissue that hold
bones together.]
14. Why do bones need cartilage pads where they meet
other bones?
[Pads of cartilage reduce friction between bones and keep
them from grinding against each other.]
15. What is the term for the point at which two bones
meet?
[Wherever two bones meet, there is a joint.]
16. Name and describe four types of joints.
[1) Hinge joints let bones move back and forth. There are
hinge joints in the fingers and elbows. 2) A saddle joint,
like that in the thumb, permits crosswise movement as
well as back-and-forth movement. 3) The pivot joint in
the neck lets the skull rotate from side to side without our
turning the whole body. 4) Ball-and-socket joints, like
those in the shoulders, permit movement in almost any
direction.]
17. What is a type of joint that does not allow movement?
[Fixed joints, like those in the skull, are locked together
so that movement is not possible.]
18. A marionette's jointed limbs are moved by strings.
What moves ours?
[Muscles make bones move.]
19. How are muscles attached to bones?
[Strong cords of tissue called tendons attach muscles to
bones.]
20. About how many muscles are there in the human body,
and approximately how much of a person's total weight is
muscle?
[There are more than 650 muscles, and they make up
almost half of a person's body weight.]
21. What are skeletal muscles?
[They are the muscles attached to bones.]
22. What are two other types of muscles?
[They are cardiac muscle, of which the heart is made,
and smooth muscle, which lines many of our internal
organs.]
23. Which types of muscles are voluntary, and which are
involuntary, and why?
[Smooth and cardiac muscle are involuntary, because
we don't consciously control them. We do consciously
control skeletal muscles, which are voluntary muscles.]
24. How do muscles work?
[They work by contracting and relaxing, and many work in
pairs. One muscle in a pair will contract while the
other relaxes.]
25. What happens to muscle cells, or fibers, when the
body is inactive?
[These cells actually decrease in size.]
26. Why is exercise so important for muscles, including
the heart muscle?
[Exercise makes muscle fibers grow larger and stronger.]
ACTIVITIES
The following activities are meant to enhance students'
understanding of topics covered in the program and to introduce them to areas not covered. *Starred activities are
adapted in large part from Blood and Guts: A Working Guide
to Your Own Insides, by Linda Allison (see bibliography).
1.
Growth of bones from infancy to adulthood: As children
grow, bones change not only in composition, but also
in relative size. Students could find out how the proportions of the bones change as a person matures.
2.
Comparing skeletons of different vertebrates: Students
could examine and compare skeletons of various
vertebrates, including mammals, fish, birds, amphibians,
and reptiles. They should explore the ways in which each
creature's skeletal structure relates its habits and its
adaptation to its environment.
3.
The structure of bones: examining animal bones. A local
butcher or supermarket may provide bones so students
can see their actual structures. Ask for long bones, like
shin bones, and ask the butcher to saw one lengthwise
and one crosswise. Examine the basic parts of the bone.
Then take the bone that has been cut lengthwise and
carefully pull away the membranous covering to expose
the layer of hard bone, and examine the surface of that
layer. (If the bone is fresh, there will be tiny red dots
where blood vessels enter the bone.) Finally, scoop out
the marrow and boil the bone to remove all traces. Examine the inner surface of the hard bone. (There will be
struts or braces that grow along lines of stress.)
You may also ask the butcher for some different kinds
of bones: rib bones, shoulder joints, and so on. Students
also could compare bones from different animals; for instance, chicken bones and steer bones. Students handling
bones should be cautioned that the bones may harbor
harmful microorganisms; they should keep their hands
away from their faces and wash their hands frequently.
Care should be taken to keep the work area clean.*
4.
The structure of bones: the role of minerals. Inorganic
materials — minerals — give bones their hardness. If
you remove minerals from bones, what remains is amazingly soft and flexible.
Students should clean some chicken bones very well
and soak them for about a week in a 6% solution of
hydrochloric or muriatic acid. (Full-strength plain
vinegar may work too.) The bones should then be rinsed
in a solution of 1 cup of water and 2 teaspoons of baking
soda to neutralize the acid. The bones will be so flexible
that they can be tied in knots. This is because the
minerals in the bones have been dissolved. RUBBER
GLOVES SHOULD BE WORN WHEN HANDLING THE
ACID AND THE BONES.
5.
The structure of bones: bone repair. An orthopedist
could be invited to speak to the group about bone breaks
and how bones repair themselves; if possible the doctor
should bring X-rays. The talk also might include
some discussion of other problems that can develop
with joints, ligaments, and tendons.
6.
The structure of bones: the strength of a cylinder. The
long bones of the legs and arms are cylindrical because a
cylinder is a form of great structural strength. Students
can explore the strength of a cylinder by rolling cylinders
of various lengths and thicknesses out of paper, fastening
them with tapes. They can "bridge" the cylinders
across two books and place weights on them to see how
well they are able to support weight, and at what point
they buckle. They can explore ways to make their cylinders stronger, and discuss whether their solutions
have any relation to the structure of bones.
Students also should stand the cylinders upright and
place weights on their ends. Does the cylinder support
more weight when it is upright or when it is horizontal?
7.
The structure of bones: dissecting a chicken leg. Students can examine a chicken leg (drumstick and thigh
attached) to find out more about the structure of
muscles, as well as how they work with bones and how
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joints make movement possible.
First, the skin of the leg should be removed — it will
peel down like a stocking. Students should notice the
feather bumps, the fat under the skin, and capillaries.
Next, students should flex the leg, noting how the
muscles move in relation to each other.
At the base of the leg are tendons. Students can slice
through these and separate the muscle groups. They
should look for large blood vessels.
Finally, students should carefully expose the joint
between the thigh and drumstick. They will see white,
sheet-like bands of ligaments; fat pads; and cartilage
pads*
Raw chicken often harbors disease organisms.
Students should keep their hands away from their faces
while working and wash their hands thoroughly after
handling the chicken.
8. Research topics: muscles and bones. The following topics
suggest possible areas for student research.
— Fossil bones: How bones become fossilized; what
can be learned from fossil bones. Carbon dating of
bones could also be explored.
— Calcium and bones: Why calcium is important to
the development of healthy bones; what happens when
calcium is deficient; what are the best sources of
dietary calcium.
— Bone growth: How is bone actually laid down?
Students could learn about the formation of bone
tissue. They also could find out about the degeneration of bones, as in osteoporosis.
— Exercise, muscles, and bones: How exercise helps
build and maintain healthy muscles and bones; what
happens to bones and muscle when we do not get
enough exercise.
— Muscle fibers for different sports: Fast-twitch and
slow-twitch muscle fibers in the skeletal muscles have
different characteristics and are suited for different
activities. Students could find out about these two
types of muscle fiber and how they can affect athletic
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performance.
— Invertebrates: Animals that are invertebrates may
have exoskeletons or no skeletons at all. Students
could learn more about this class of animals, perhaps
choosing a particular type of invertebrate to research.
— The major bones and their names: What are the
major bones of the human body and what are their
names?
— The major muscles and their names: What are the
human body's major muscles and what are their
names?
— Marrow and the immune system: People with immune deficiencies are sometimes given bone marrow
transplants in the hope that this will bolster their
immune systems. Students could explore the connections between bone marrow and the immune system.
SCRIPT
Narrator: One of the most striking examples of the strength
and flexibility of the human body can be found in the formal
discipline known as karate.
It takes years of dedicated practice to achieve the level of
perfection demonstrated by a person who has achieved a
black belt in karate.
But the performance of karate also points to systems of
the human body that all people share.
It is the bones of the skeletal system that give the body
shape, structure, and protection, and the muscles attached to
this flexible framework of bones give the body mobility and
strength.
Our Flexible Frame: The Skeletal and Muscular Systems
Narrator: Painting a picture depends no less on the body's
skeletal and muscular systems than does the performance of
karate. Each delicate stroke of the brush requires finely
coordinated actions of muscles and bones in the fingers,
hand, and wrist.
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in fact, anything we do involves our muscular and skeletal
systems. Even standing still requires the support of bones
and muscles to prevent us from falling over. And muscles
are constantly working as we breathe and as our hearts beat.
For the moment, let's focus on the skeletal system, the
body's internal framework of bones. These bones have many
shapes and sizes.
The largest bones are the two femurs or thigh bones. For
their weight, in fact, the femurs are much stronger than steel.
Because they are very strong, the femurs can support our
weight — while running or jumping, for example.
In contrast to the femurs, the smallest bones in the body
are three tiny, delicate bones deep inside the ear. Sound waves
cause these bones to vibrate and send signals to the brain.
It is this process that enables us to hear many different
sounds in the world around us.
In the human hand alone there are 27 different bones.
Working together, these bones make it possible to hold and
work with a brush, pencil, or tool.
All together, there are 206 different bones in the body of
an adult, but we are born with more.
This baby, in fact, was born with about three hundred bones.
But some of these bones grow together, or fuse.
A baby's bones are very soft and flexible because they consist
mostly of a material called cartilage. But as a baby grows,
hard bone gradually replaces most of this cartilage. In the
process, her bones will get larger.
Let's take a look at a single bone and see how it changes
and grows over time. We'll look at the tibia, or shin bone.
Before birth, in the human fetus most of this bone is cartilage,
which we show here in the color blue. Already, however, some
hard bone tissue has begun to form in the center of the bone.
After birth, as the bone grows, new cartilage is formed and
then replaced by hard bone. In this way, the bone gets bigger.
This process continues through childhood, although it
slows somewhat during later childhood.
But then it speeds up dramatically in the teenage years
when there is a growth spurt. By the late teens, growth stops.
Most cartilage will have been completely replaced by hard
bone.
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Despite the fact that bones grow, this is how we often think of
bones — as being hard, brittle, and not alive — like the
skeleton of a long dead animal.
But bones are very much a living part of us, just like other
tissues in the body such as those of the skin and heart. And
we need the skeletal system to engage in the full range of
activities that make up our daily lives.
Looking at a thin slice of bone under a microscope, we can
see circular layers of hard bone tissue. These layers consist
of minerals, mainly calcium and phosphorus. Embedded between the layers are bone cells. The dark spots in the center
of the circles are canals containing blood vessels.
Because calcium and phosphorus help build strong bones, it
is important to eat foods that contain these minerals —
foods like milk.
Let's take a look at the structure of a bone, in this case a
femur, or thigh bone. . . If you could peel away the outer
part of this bone, you'd see that it consists of a hard and
tough membrane. When you break a bone, cells from this
layer help repair the break.
In the shaft of the femur, beneath the outer membrane,
there is a layer of hard bone called compact bone. Compact
bone gives bones their strength. . . .
Extending through the center of the shaft is a cavity. While
compact bone makes the femur strong, this cavity makes it
light.
Inside the cavity there is a soft yellow tissue called yellow
marrow. This tissue contains fat that stores energy.
If we looked at the ends of a long bone such as the femur,
we'd see a different kind of bony tissue, called spongy bone.
Spongy bone contains large spaces, like a honeycomb.
Inside these spaces, there is another kind of marrow, red
marrow. As you will soon see, red marrow has a very important
function.
The more we learn about the bones of the skeletal system,
the more important they seem. The skeletal system serves
several functions.
For one thing, bones give our bodies shape and support.
Our skeletal systems help give us our human form. We look
different from an elephant or a bird in part because of the
different shapes of our skeletons.
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We also look different from each other partly because of
our skeletal systems. We are tall or short or in between
because of the size and shape of our bones. Have you ever
thought of what we'd look like if it weren't for our skeletons?
We'd be like a mass of jelly. We'd have no shape or form,
and we'd be unable to stand without the internal support of
our bones.
A second important function of the skeletal system is that it
protects the important internal organs of the body.
Consider the brain. The brain coordinates all our conscious
and unconscious activities. If the brain were damaged, a person
might lose important capabilities. He or she might become
blind, be unable to speak, lose the power of memory, or even
die.
But the brain has some very effective protection — the
skull. The skull is like a helmet that surrounds the brain.
The top of the skull forms a dome — a shape that is very
strong and can withstand heavy blows.
Extending from the base of the brain and at the back of
the body is the spinal cord, an elongated bundle of nerve
tissues that branch out and carry messages between the brain
and the other parts of the body.
The spinal cord, too, has very good protection. The skull
rests on another part of the skeletal system, the spinal column. The spinal column is made up of 33 bones called
vertebrae.
Each vertebrae has a ring-like shape. Together these
vertebrae form a flexible tube through which the spinal cord
passes, protected from possible injury.
Attached to the upper vertebrae are twelve pairs of arched
bones called ribs.
Most of these ribs are joined in the front by cartilage to a
shield-like bone called the sternum, or breastbone.
The ribs, sternum, and vertebrae together form a kind of
cage that protects vital organs in the chest, including the
heart and the lungs.
A third function of the skeletal system is one that is not
readily apparent. But this function is vitally important to
the human body. The skeletal system produces blood cells.
We saw earlier that inside some bones, particularly the
bones of the arms and legs, is soft tissue called red marrow.
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This tissue manufactures blood cells.
One type of blood cell that red marrow produces is red
blood cells. Red blood cells carry oxygen from the lungs
throughout the body. But these hard-working red blood cells
have a lifespan of only about 125 days before they start to
break down. However, red marrow manufactures new red
blood cells at the rate of 2 million a second, insuring that
our bodies have an adequate supply.
The fourth major function of the skeletal system is one
that we've already seen. The skeletal system provides a flexible
framework to which muscles are attached, allowing the body
to move.
We may most appreciate the body's flexibility when admiring
different types of athletic performance, but even the
simplest of tasks usually depends on the body being able
to move.
Bones are connected to each other in ways that allow the
skeleton to bend and twist and move in many different ways.
Look at the legs of a cyclist. The cyclist can bend his legs
because each leg has not one bone, but several bones.
Let's look more closely at these bones. The femur, or thigh
bone, connects at the knee with two bones called the tibia
and fibula and also with the bone that forms the knee cap.
The bones of the leg are held together by tough bands of
tissue called ligaments. Ligaments are flexibile enough to
allow the bones to move.
The ends of the bones are also covered with pads of cartilage. The cartilage pads reduce friction between bones and
prevent them from grinding each other down.
Whenever two bones meet, a joint is formed. To see how
some different types of joints work, let's observe some of
the different movements a baseball pitcher makes.
To grasp the ball, he puts his fingers around it and holds it
firmly in his hand.
He may turn his head to look over at first base.
As he winds up and throws, he bends his arms and legs,
hurling the ball toward the batter.
None of these actions would be possible without different
kinds of joints.
The hand, for example, has several kinds of joints. The
fingers have joints that allow them to move back and forth.
16
Such joints are called hinge joints because they are like the
hinges of a door or gate.
The thumb can move freely across the palm of the hand
because of a special kind of joint called the saddle joint.
The saddle joint gives the thumb great flexibility.
Together hinge and saddle joints make the hand agile at
grasping things. Without these joints, we couldn't hold a
baseball or write with a pencil.
The skull can rotate from side to side because of another
kind of joint between the first and second vertebrae. This is
known as the pivot joint.
The pivot joint allows us to look in different directions
without having to turn the whole body.
The end of the long bone of the pitcher's arm has a
rounded, ball-shaped knob that fits into a cup-shaped socket in
the shoulder blade. This is called a ball-and-socket joint.
The ball-and-socket joint allows the arm to move freely in
almost any direction.
The arm's elbow is another example of a hinge joint. While it
allows only back-and-forth movement, it is more stable and
gives us more control.
Together the arm's different joints help make it possible
to throw a ball with accuracy and power.
Sometimes bones are joined together in a way that doesn't
allow movement. Most of the bones of the skull, for example,
are locked firmly together by zig-zag joints called fixed joints.
Such joints make the skull a strong helmet that protects us
from injury.
In some ways, bones and joints are like the wooden arms
and legs of a marionette. The stick-like parts of the
marionette are joined together with hinges that allow an
almost human-like flexibility.
But the marionette's arms and legs don't move by themselves. They need someone to pull the strings that are attached to them.
Like the wooden parts of a marionette, the bones of the
human skeleton also cannot move by themselves.
But instead of having strings, bones have muscles attached
to them.
Muscles and bones are joined by strong cords of tissue
called tendons. Tendons enable muscles to move bones. For
17
example, when this muscle in the upper arm contracts, it pulls
on a tendon that is attached to a bone in the lower arm. The
lower arm is raised.
Any kind of body movement depends on muscles. Muscles
in the leg provide the power for a karate kick.
Muscles in the hand and arm allow us to use a hammer.
There are more than 30 skeletal muscles attached to the
skull and facial skin alone. These facial muscles signal our
moods to other people in many different ways.
Muscles in the comer of the mouth make it possible to
smile.
Or exhibit surprise.
Muscles around the mouth and eyes display sadness.
Muscles in the forehead help us frown with disapproval.
Or anger.
Even when we are not moving, muscles are important.
Standing still requires the use of muscles in the calves that
help support the body's weight. If you've ever had to stand
still for a long time, you know how tired these muscles can
get.
All together there are more than 650 different muscles in
the human body. If you weigh 80 pounds, chances are that
your body has almost 45 pounds of muscles, for muscles
make up almost half of a person's body weight.
Up to now, the muscles we've talked about have all been
of one kind. They are called skeletal muscles because they
are attached to bones.
But there are two different kinds of muscles as well. Most
of the heart is made up of muscle. This muscle is called cardiac muscle. Cardiac muscle keeps the heart beating
throughout a person's lifetime, insuring that the body has
an adequate supply of blood.
Another type of muscle is called smooth muscle. Smooth
muscle lines internal organs, such as the stomach and intestines, and the walls of blood vessels. Among other things,
they help move food through the digestive tract and control
the flow of blood through arteries and veins.
Both smooth and cardiac muscles are called involuntary
muscles because we can't directly control them.
We can't control how our stomach muscles work. After we
eat an apple, these muscles churn and squeeze the food
18
without our having to think about it.
But skeletal muscles are different. They are called "voluntary" because you can consciously control them. A painter,
for example, holds and moves her brush very deliberately in
order to get the effects she wants.
Of course, most of the time we don't think so deliberately
about every movement we make. With practice and repetition, many movements become almost second nature. Our
brain coordinated the activities of our skeletal muscles
without our having to think about it.
Muscles work by contracting and relaxing. Because of the
way muscles contract, skeletal muscles attached to bones can
only pull, they cannot push. For this reason, many skeletal
muscles work in pairs. One muscle will bend a joint while
the other straightens it.
Let's look at the muscles in the arm to see how this works. In
this illustration, notice how the biceps muscle on top and
triceps muscle underneath are each attached to the bones of
both the upper and lower arm.
When the biceps muscle contracts, it gets shorter and pulls
the forearm bone up like a lever.
When the triceps contracts and the biceps relaxes, the arm
is pulled down again.
Other muscles in the body work the same way. Whenever
you bend, or twist, or move your body in any way, pairs of
muscles are at work as one muscle contracts while the other
relaxes.
But if muscles aren't used, they will become weak and
flabby.
Like everything else in the body, muscles are made up of
cells. But muscle cells, which are also called fibers, will actually decrease in size if they are not active.
With exercise, these same cells become larger. Stronger
'muscles can do more work without getting tired.
And this isn't just true of muscles that we can see most
easily, like those in the arms and legs. The heart muscle can
be made stronger with exercise. Running, bicycling, and
swimming are among the activities that require the heart to
work harder, thus strengthening it. A strong heart can work
more efficiently and help us have more energy and live longer.
19
SUMMARY
In this program we've looked at many different things about
the skeletal and muscular systems.
We've seen how the body's muscles and bones work
together in ways that give the body flexibility, power, and
grace.
We've seen that the skeletal system consists of bones of
many sizes and shapes that serve a variety of functions —
from the large femurs, or thigh bones, that help support our
weight. . .
To the tiny bones in the ear that enable us to hear.
We've seen that a baby's bones are soft and flexible because
their bones are still mostly made of cartilage, and that as a
baby grows most of this cartilage will be replaced by hard
bone.
We've looked at the structure of bones and the different
things that make up bones, such as compact bone that gives
bones strength.. .and yellow marrow that stores energy.
We've seen that the skeletal system serves several important
functions. It gives our body shape and support.
It protects internal organs from injury.
The red marrow of bones manufactures blood cells.
And it provides a place of attachment for muscles, making
it possible for the body to move.
We've looked at some of the different kinds of joints that
are part of the skeletal system, and we've seen how these
joints make possible different kinds of movement.
We've examined the different kinds of muscles in the body,
including skeletal muscles that are attached to bones and
make it possible to flex an arm, and even to breathe; cardiac
muscles that make it possible for the heart to beat; and
smooth muscles that line our internal organs.
We've seen how muscles function by contracting and relaxing.
And how muscles get larger and stronger as a result of
exercise.
Our skeletal and muscular systems make it possible for
us to move.. .to play. . .to actively enjoy the world around us.
THE END.
20
CREDITS
Author and Producer
Peter Cochran
Graphics and Animation
Luba Semenec
Director of Photography
Peter Scheer
Additional Photography
Deerfield Video
Stock Video
Killington, Ltd.
Photo Researchers, Inc.
Narrator Gene
Galusha
Post Production
Deerfield Video
Audio Sweetening Acme
Recording Studios
GLOSSARY
Ball-and-socket joint: a type of joint found in the shoulder
and hip; it allows movement in many different directions.
Bones: the hard, strong, somewhat flexible components of
the skeletal system; they support and give shape to the body
and, in conjunction with muscles, make movement possible.
Brain: the organ that coordinates the processes of the body;
the control center of our conscious and unconscious thoughts
and activities.
Calcium: a mineral that is an important component of bones,
giving them hardness and strength.
Cardiac muscle: the type of muscle of which the heart is
made.
21
Cartilage: a rubbery, flexible tissue that, like bone, gives the
body shape and protection, but lacks the hardness and
strength of bone. Cartilage pads serve to cushion and protect
our joints.
Cells: the units of which all living tissue are composed.
Compact bone: A hard, dense type of bone; it is found in
the shafts of the long bones of the body.
Femur: the thigh bone.
Fetus: an unborn child, from about the age of three months
to birth.
Fibula: one of the bones of the calf of the leg.
Fixed joint: an immoveable joint, such as the joints that occur
in the cranium of the skull.
Growth spurt: a period of peak growth during the preteen
and teenage years. For girls, this occurs between the ages of
about 10 and 14; for boys, between about 12 and 16.
Hinge joints: a type of joint that allows back-and-forth movement; found in the fingers and elbows.
Involuntary muscles: muscles that function without our consciously controlling them; for instance, the muscles of the
stomach and intestines.
Knee cap (patella): the small triangular bone that forms the
front of the knee and protects the knee joint.
Ligaments: strong, flexible bands of tissue that connect
bones to other bones.
Minerals: inorganic compounds, like calcium and phosphorus.
Muscular system: the system of body tissues called muscles,
which produce motion. These include voluntary, cardiac,
and smooth muscles.
Phosphorus: a mineral that helps give bones their hardness
and strength.
Pivot joint: a type of joint that allows rotating movement;
found in the neck.
22
Red marrow: a type of soft tissue found in the ends of the
long bones of the body. Red marrow produces red blood cells.
Red blood cells: the blood cells that carry oxygen throughout
the body.
Ribs: the narrow bones of the chest that form the rib cage,
which surrounds and protects vital organs, including the heart
and liver.
Saddle joints: a type of joint found in the thumb, which allows
for lateral movement as well as back-and-forth movement.
Skeletal muscles: the muscles that compose most of our
flesh. They usually are attached to bones, and they allow for
voluntary movement.
Skeletal system: the system of bones that forms a flexible
framework for the body and produces red blood cells.
Skull: the bones of the head, which encase the brain and
give structure to the face.
Smooth muscles: a type of muscle that lines some of our
internal organs, such as the stomach and intestines.
Spinal cord: a long, cordlike bundle of nerve tissues extending
from the brain down the back. The brain and spinal cord
together form the central nervous system.
Spinal column: the column of bones, called vertebrae, that
encases and protects the spinal cord.
Spongy bone: a type of bone tissue found in the ends of the
long bones of the body and in certain other bones. Spongy
bone is filled with honeycomb spaces that contain red marrow.
Sternum: also called the breastbone, at the front of the chest,
serves as a point of connection for most of the ribs.
Tendons: tough, fibrous bands of tissue that connect muscles
to bone.
Tibia: the larger of the two bones of the lower leg, between
the knee and the ankle.
Vertebrae: the bones that compose the spinal column, which
encases the spinal cord.
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Voluntary muscles: the skeletal muscles that we consciously
control to produce the movements we desire.
Yellow marrow: a type of soft tissue in the core of the long
bones of the body. This fatty tissue stores energy.
BIBLIOGRAPHY
Allison, Linda, Blood and Guts: A Working Guide to Your
Own Insides. Boston: Little, Brown and Company, 1976.
Broekel, Ray, Your Skeleton and You. Chicago: Children's
Press, 1984.
Bruun, Ruth Dowling, M.D. and Bruun, Bertel, M.D., The
Human Body: Your Body and How It Works. New York:
Random House, Inc., 1984.
Elgin, Kathleen, The Human Body: The Skeleton. New
York: Franklin Watts, Inc., 1971.
Gallant, Roy A., Me and My Bones. Garden City, Mew York:
Doubleday & Company, Inc., 1971.
Gaskin, John, Movement. New York: Franklin Watts, 1984.
Samachson, Joseph, The Armor Within Us: The Story of
Bone. Chicago: Rand McNally & Company, 1966.
Silverstein, Dr. Alvin and Silverstein, Virginia B., The Skeletal
System: Frameworks for Life. Englewood Cliffs, New
Jersey: Prentice-Hall, Inc., 1972.
Vevers, Dr. Gwynne, Your Body: Muscles and Movement.
New York: Lothrop, Lee & Shepard Books, 1984.
Vevers, Dr. Gwynne, Your Body: Skin and Bones. New York:
Lothrop, Lee & Shepard Books, 1983.
Weart, Edith Lucie, The Story of Your Bones. New York:
Coward-McCann, Inc., 1966.
Zim, Herbert S., Bones. New York: William Morrow and
Company, 1969.
24
Related Videos from Rainbow
Body's Defenses Against Disease Breath of Life:
Our Respiratory System Cell Division
Food into Fuel: Our Digestive System In
Control: Our Brain and Nervous System
Introducing the Cell
Our Flexible Frame: The Muscular and Skeletal
Systems
Pumping Life: The Heart and Circulatory System
25
CLOZE EVALUATION QUESTIONS
OUR FLEXIBLE FRAME: THE SKELETAL AND MUSCULAR SYSTEMS
NAME
DIRECTIONS: Select the answer from the four choices given by circling the correct letter.
1. Together our skeletal and muscular system give our body shape and allow us to walk
and run. An important job of the bones is _ the internal organs of the body. These include
such organs as the lungs and heart.
1. (
(B)
(C)
(D)
to protect
to shape
to restrict
to grow
2. We must have a balanced diet for our bones and muscles to develop. Vitamins and minerals such as 2. (A) niacin
_ help bones to grow and become strong. Foods such as milk and dairy products are rich in these (B) calcium
(C) iron zinc
minerals.
(D) spongy
3. There are different kinds of bones in the human body. One kind called _ is very strong yet light in 3. (A) bone
weight. This type of bone gives us freedom of movement which is so important in the many sports we (B)
(C)
enjoy.
4. Our blood system supplies all of the body's cells with food and oxygen. The red blood cells which (D)
carry the oxygen are produced in the _ of the bones. This is a very important function of the bones 4. (A)
since red blood cells are used up and must be constantly replaced.
(B)
cartilage
compact bone
long bone
yellow marrow
red tissue
(C) white marrow
(D) red marrow
5. Specific bones have a special job in protecting the internal organs within our bodies. The brain is
protected by the _. This type of bone covers the brain tike a helmet and cushions it against any injury. 5. (A) skull
(B) ribs
6. Another series of bones protects the spinal cord. The _ which is made up of vertebra prevents injury (C) spinal column
(D) sternum
to the spinal cord. The spinal cord is responsible for all body movement.
7. A series of bones which looks like a cage protects other body parts. The _ guard the lungs and
6. (A) skull
heart against injury.
(B) spinal column
(C) skeletal
ribs
8. (A)
8. The muscular system enables the bones to move in various ways. Those specific muscles
(D) cardiac
sternum
(B)
that are attached to bones are called _ muscles. They are found throughout all parts of our
(C) smooth
body.
7. (A)
skull
(D)
(B) voluntary
spinal column
(C) skeletal
ribs
9. (A)
9. Another set of muscles assist the heart. The _ muscles keep the heart beating throughout
sternum
(D)
(B) smooth
our lives. They consist of strong bands of muscles that wrap around the heart.
(C) voluntary
(D) cardiac
10. A third kind of muscle is found inside of various internal organs. The _ type of muscle
tissue is found inside of our stomachs and blood vessels. They are strong and assist the
movement of liquids through these organs.
This form may be reproduced without receiving permission from Rainbow Educational Video.
10. (A) skeletal
(B) smooth
(C) voluntary
(D) cardiac