NCERT Textbook Class 8 - Body Movements, Class 6,Science | EduRev Notes

Science & Technology for UPSC CSE

UPSC : NCERT Textbook Class 8 - Body Movements, Class 6,Science | EduRev Notes

 Page 1


66 SCIENCE
8
Body Movements
S
it absolutely still. Observe the
movements taking place in your
body. You must be blinking your
eyes, time to time. Observe the
movements in your body as you
breathe. There are so many movements
that happen in our bodies.
When you are writing in your
notebook which part of the body are you
moving? Or, when you turn and look at
your friend? Different parts of your body
move while you remain at the same
place, in these examples. You also move
from one place to another — you get up
and go to your teacher or to the school
compound, or go home after school. You
walk, run, skip, jump and move from
place to place.
Let us see how animals move from
place to place by filling up Table 8.1,
after discussing with our friends,
teachers and parents.
Walk, run, fly, jump, creep, crawl,
slither and swim – these are only a few
of the ways in which animals move from
one place to another. Why are there so
many differences in the way that
animals move from place to place? Why
is it that many animals walk while a
snake slithers or crawls and a fish
swims?
8.1 HUMAN BODY AND ITS MOVEMENTS
Let us look closely at some of our own
movements to begin with, before looking
at all these varieties of movements in
animals.
Do you enjoy doing physical exercise
at school? How do you move your hands
and legs while doing different exercises?
Table 8.1 How do animals move
from place to place?
l a m i n A
d e s u t r a p y d o B
g n i v o m r o f
o t e c a l p m o r f
e c a l p
s e o d w o H
l a m i n a e h t
? e v o m
w o C s g e L k l a W
s n a m u H
e k a n S y d o b e l o h W r e h t i l S
d r i B
t c e s n I
h s i F
Boojho wonders about movements
in plants. He knows they do not
move from place to place, but, do
they show any other kind of
movements?
2020-21
Page 2


66 SCIENCE
8
Body Movements
S
it absolutely still. Observe the
movements taking place in your
body. You must be blinking your
eyes, time to time. Observe the
movements in your body as you
breathe. There are so many movements
that happen in our bodies.
When you are writing in your
notebook which part of the body are you
moving? Or, when you turn and look at
your friend? Different parts of your body
move while you remain at the same
place, in these examples. You also move
from one place to another — you get up
and go to your teacher or to the school
compound, or go home after school. You
walk, run, skip, jump and move from
place to place.
Let us see how animals move from
place to place by filling up Table 8.1,
after discussing with our friends,
teachers and parents.
Walk, run, fly, jump, creep, crawl,
slither and swim – these are only a few
of the ways in which animals move from
one place to another. Why are there so
many differences in the way that
animals move from place to place? Why
is it that many animals walk while a
snake slithers or crawls and a fish
swims?
8.1 HUMAN BODY AND ITS MOVEMENTS
Let us look closely at some of our own
movements to begin with, before looking
at all these varieties of movements in
animals.
Do you enjoy doing physical exercise
at school? How do you move your hands
and legs while doing different exercises?
Table 8.1 How do animals move
from place to place?
l a m i n A
d e s u t r a p y d o B
g n i v o m r o f
o t e c a l p m o r f
e c a l p
s e o d w o H
l a m i n a e h t
? e v o m
w o C s g e L k l a W
s n a m u H
e k a n S y d o b e l o h W r e h t i l S
d r i B
t c e s n I
h s i F
Boojho wonders about movements
in plants. He knows they do not
move from place to place, but, do
they show any other kind of
movements?
2020-21
67 BODY MOVEMENTS
Let us try some of the many movements,
our body is capable of.
Bowl an imaginary ball at an
imaginary wicket. How did you move
your arm? Did you rotate it at the
shoulder in a circular movement? Did
your shoulder also move? Lie down and
rotate your leg at the hip. Bend your
arm at the elbow and the leg at the knee.
Stretch your arm sideways. Bend your
arm to touch your shoulder with your
fingers. Which part of your arm did you
bend? Straighten your arm and try to
bend it downwards. Are you able to
do it?
Try to move the various parts of your
body and record their movements in
Table 8.2.
Why is it that we are able to move a
few parts of our body easily in various
directions and some only in one
direction? Why are we unable to move
some parts at all?
Activity 1
Place a scale length-wise on your arm
so that your elbow is in the centre
(Fig. 8.1).
Ask your friend to tie the scale and
your arm together. Now,
try to bend your elbow.
Are you able to do it?
Table 8.2 Movements in our body
s e t a t o R
y l e t e l p m o c
s e t a t o R
s n r u t / y l t r a p
s d n e B s t f i L
t o n s e o D
l l a t a e v o m
k c e N s e Y
t s i r W
r e g n i F
e e n K
e l k n A
e o T
k c a B
d a e H
w o b l E
m r A s e Y
Fig. 8.1 Can you bend your
arm now?
Body Part
Movement
2020-21
Page 3


66 SCIENCE
8
Body Movements
S
it absolutely still. Observe the
movements taking place in your
body. You must be blinking your
eyes, time to time. Observe the
movements in your body as you
breathe. There are so many movements
that happen in our bodies.
When you are writing in your
notebook which part of the body are you
moving? Or, when you turn and look at
your friend? Different parts of your body
move while you remain at the same
place, in these examples. You also move
from one place to another — you get up
and go to your teacher or to the school
compound, or go home after school. You
walk, run, skip, jump and move from
place to place.
Let us see how animals move from
place to place by filling up Table 8.1,
after discussing with our friends,
teachers and parents.
Walk, run, fly, jump, creep, crawl,
slither and swim – these are only a few
of the ways in which animals move from
one place to another. Why are there so
many differences in the way that
animals move from place to place? Why
is it that many animals walk while a
snake slithers or crawls and a fish
swims?
8.1 HUMAN BODY AND ITS MOVEMENTS
Let us look closely at some of our own
movements to begin with, before looking
at all these varieties of movements in
animals.
Do you enjoy doing physical exercise
at school? How do you move your hands
and legs while doing different exercises?
Table 8.1 How do animals move
from place to place?
l a m i n A
d e s u t r a p y d o B
g n i v o m r o f
o t e c a l p m o r f
e c a l p
s e o d w o H
l a m i n a e h t
? e v o m
w o C s g e L k l a W
s n a m u H
e k a n S y d o b e l o h W r e h t i l S
d r i B
t c e s n I
h s i F
Boojho wonders about movements
in plants. He knows they do not
move from place to place, but, do
they show any other kind of
movements?
2020-21
67 BODY MOVEMENTS
Let us try some of the many movements,
our body is capable of.
Bowl an imaginary ball at an
imaginary wicket. How did you move
your arm? Did you rotate it at the
shoulder in a circular movement? Did
your shoulder also move? Lie down and
rotate your leg at the hip. Bend your
arm at the elbow and the leg at the knee.
Stretch your arm sideways. Bend your
arm to touch your shoulder with your
fingers. Which part of your arm did you
bend? Straighten your arm and try to
bend it downwards. Are you able to
do it?
Try to move the various parts of your
body and record their movements in
Table 8.2.
Why is it that we are able to move a
few parts of our body easily in various
directions and some only in one
direction? Why are we unable to move
some parts at all?
Activity 1
Place a scale length-wise on your arm
so that your elbow is in the centre
(Fig. 8.1).
Ask your friend to tie the scale and
your arm together. Now,
try to bend your elbow.
Are you able to do it?
Table 8.2 Movements in our body
s e t a t o R
y l e t e l p m o c
s e t a t o R
s n r u t / y l t r a p
s d n e B s t f i L
t o n s e o D
l l a t a e v o m
k c e N s e Y
t s i r W
r e g n i F
e e n K
e l k n A
e o T
k c a B
d a e H
w o b l E
m r A s e Y
Fig. 8.1 Can you bend your
arm now?
Body Part
Movement
2020-21
68 SCIENCE
Did you notice that we are able to bend
or rotate our body in places where two
parts of our body seem to be joined
together — like elbow, shoulder or neck?
These places are called joints. Can you
name more such joints? If our body has
no joints, do you think it would be
possible for us to move in any way at all?
What exactly is joined together at
these joints?
Press your fingers against the top of
your head, face, neck, nose, ear, back of
the shoulder, hands and legs including
the fingers and toes.
Do you get a feel of something hard
pressing against your fingers?  The hard
structures are the bones. Repeat this
activity on other parts of your body. So
many bones!
Bones cannot be bent. So, how do
we bend our elbow? It is not one long
bone from the upper arm to our wrist. It
is different bones joined together at the
elbow. Similarly, there are many bones
present in each part of the body.  We
can bend or move our body only at those
points where bones meet.
There are different types of joints in
our body to help us carry out different
movements and activities. Let us learn
about some of them.
Ball and socket joints
Activity 2
Roll a strip of paper into a cylinder. Make
a small hole in an old rubber or plastic
ball (under supervision) and push the
paper cylinder into it as shown in
Fig. 8.2. You can also stick the cylinder
on the ball. Put the ball in a small bowl.
Does the ball rotate freely inside the bowl?
Does the paper cylinder also rotate?
Now, imagine that the paper cylinder
is your arm and the ball is its end. The
bowl is like the part of the shoulder to
which your arm is joined. The rounded
end of one bone fits into the cavity
(hollow space) of the other bone
(Fig.8.3). Such a joint allows movements
in all directions.  Can you name another
such joint you can think of, recollecting
the body movements we tried at the
beginning of this section?
Pivotal Joint
The joint where our neck joins the head
is a pivotal joint (Fig. 8.4). It allows us
to bend our head forward and backward
and turn the head to our right or left.
Try these movements. How are these
movements different from those of our
arm that can rotate a complete circle in
Fig. 8.3 A ball and socket joint
Thigh Bone
Hip Bone
Fig. 8.2 Making a ball and socket joint
Ball and
Socket Joint
Bowl
Ball
Paper Cylinder
2020-21
Page 4


66 SCIENCE
8
Body Movements
S
it absolutely still. Observe the
movements taking place in your
body. You must be blinking your
eyes, time to time. Observe the
movements in your body as you
breathe. There are so many movements
that happen in our bodies.
When you are writing in your
notebook which part of the body are you
moving? Or, when you turn and look at
your friend? Different parts of your body
move while you remain at the same
place, in these examples. You also move
from one place to another — you get up
and go to your teacher or to the school
compound, or go home after school. You
walk, run, skip, jump and move from
place to place.
Let us see how animals move from
place to place by filling up Table 8.1,
after discussing with our friends,
teachers and parents.
Walk, run, fly, jump, creep, crawl,
slither and swim – these are only a few
of the ways in which animals move from
one place to another. Why are there so
many differences in the way that
animals move from place to place? Why
is it that many animals walk while a
snake slithers or crawls and a fish
swims?
8.1 HUMAN BODY AND ITS MOVEMENTS
Let us look closely at some of our own
movements to begin with, before looking
at all these varieties of movements in
animals.
Do you enjoy doing physical exercise
at school? How do you move your hands
and legs while doing different exercises?
Table 8.1 How do animals move
from place to place?
l a m i n A
d e s u t r a p y d o B
g n i v o m r o f
o t e c a l p m o r f
e c a l p
s e o d w o H
l a m i n a e h t
? e v o m
w o C s g e L k l a W
s n a m u H
e k a n S y d o b e l o h W r e h t i l S
d r i B
t c e s n I
h s i F
Boojho wonders about movements
in plants. He knows they do not
move from place to place, but, do
they show any other kind of
movements?
2020-21
67 BODY MOVEMENTS
Let us try some of the many movements,
our body is capable of.
Bowl an imaginary ball at an
imaginary wicket. How did you move
your arm? Did you rotate it at the
shoulder in a circular movement? Did
your shoulder also move? Lie down and
rotate your leg at the hip. Bend your
arm at the elbow and the leg at the knee.
Stretch your arm sideways. Bend your
arm to touch your shoulder with your
fingers. Which part of your arm did you
bend? Straighten your arm and try to
bend it downwards. Are you able to
do it?
Try to move the various parts of your
body and record their movements in
Table 8.2.
Why is it that we are able to move a
few parts of our body easily in various
directions and some only in one
direction? Why are we unable to move
some parts at all?
Activity 1
Place a scale length-wise on your arm
so that your elbow is in the centre
(Fig. 8.1).
Ask your friend to tie the scale and
your arm together. Now,
try to bend your elbow.
Are you able to do it?
Table 8.2 Movements in our body
s e t a t o R
y l e t e l p m o c
s e t a t o R
s n r u t / y l t r a p
s d n e B s t f i L
t o n s e o D
l l a t a e v o m
k c e N s e Y
t s i r W
r e g n i F
e e n K
e l k n A
e o T
k c a B
d a e H
w o b l E
m r A s e Y
Fig. 8.1 Can you bend your
arm now?
Body Part
Movement
2020-21
68 SCIENCE
Did you notice that we are able to bend
or rotate our body in places where two
parts of our body seem to be joined
together — like elbow, shoulder or neck?
These places are called joints. Can you
name more such joints? If our body has
no joints, do you think it would be
possible for us to move in any way at all?
What exactly is joined together at
these joints?
Press your fingers against the top of
your head, face, neck, nose, ear, back of
the shoulder, hands and legs including
the fingers and toes.
Do you get a feel of something hard
pressing against your fingers?  The hard
structures are the bones. Repeat this
activity on other parts of your body. So
many bones!
Bones cannot be bent. So, how do
we bend our elbow? It is not one long
bone from the upper arm to our wrist. It
is different bones joined together at the
elbow. Similarly, there are many bones
present in each part of the body.  We
can bend or move our body only at those
points where bones meet.
There are different types of joints in
our body to help us carry out different
movements and activities. Let us learn
about some of them.
Ball and socket joints
Activity 2
Roll a strip of paper into a cylinder. Make
a small hole in an old rubber or plastic
ball (under supervision) and push the
paper cylinder into it as shown in
Fig. 8.2. You can also stick the cylinder
on the ball. Put the ball in a small bowl.
Does the ball rotate freely inside the bowl?
Does the paper cylinder also rotate?
Now, imagine that the paper cylinder
is your arm and the ball is its end. The
bowl is like the part of the shoulder to
which your arm is joined. The rounded
end of one bone fits into the cavity
(hollow space) of the other bone
(Fig.8.3). Such a joint allows movements
in all directions.  Can you name another
such joint you can think of, recollecting
the body movements we tried at the
beginning of this section?
Pivotal Joint
The joint where our neck joins the head
is a pivotal joint (Fig. 8.4). It allows us
to bend our head forward and backward
and turn the head to our right or left.
Try these movements. How are these
movements different from those of our
arm that can rotate a complete circle in
Fig. 8.3 A ball and socket joint
Thigh Bone
Hip Bone
Fig. 8.2 Making a ball and socket joint
Ball and
Socket Joint
Bowl
Ball
Paper Cylinder
2020-21
69 BODY MOVEMENTS
its ball and socket joint? In a pivotal
joint a cylindrical bone rotates in a ring.
Hinge joints
Open and close a door a few times.
Observe the hinges of the door carefully.
They allow the door to move back
and forth.
Activity 3
Let us look at the kind of movement
allowed by a hinge. Make a cylinder with
cardboard or thick chart paper, as
shown in Fig. 8.5. Attach a small pencil
to the cylinder by piercing the cylinder
at the centre, as shown. Make a hollow
half cylinder from cardboard such that
the rolled up cylinder can fit inside it
easily. The hollow half cylinder with the
rolled up cylinder sitting inside it, allows
movement like a hinge. Try to move the
rolled up cylinder. How does it move?
How is this movement different from
what we saw with our constructed ball
and socket joint? We saw this kind of
movement at the elbow in Activity 1.
What we have constructed in Fig. 8.5 is
different from a hinge, of course. But, it
illustrates the direction in which a hinge
allows movement. The elbow has a hinge
joint that allows only a back and forth
movement (Fig. 8.6). Can you think of
more examples of such joints?
Fixed joints
Some joints between bones in our head
are different from those we have
discussed so far. The bones cannot move
at these joints. Such joints are called
fixed joints. When you open your
mouth wide, you can move your lower
jaw away from your head, isn’t it? Try
to move your upper jaw, now. Are you
able to move it? There is a  joint between
the upper jaw and the rest of the head
which is a fixed joint.
We discussed only some of the joints
that connect parts of our body.
What gives the different parts of the
body their different shapes?
If you wanted  to make a doll, what
will you make first? Perhaps a
framework to give the doll shape before
making its outer structure, isn’t it? All
the bones in our body also form a
framework to give a shape to our body.
Fig. 8.5 Fig. 8.5 Fig. 8.5 Fig. 8.5 Fig. 8.5 Directions of movement allowed by a hinge
like joint
Fig. 8.6 Fig. 8.6 Fig. 8.6 Fig. 8.6 Fig. 8.6 Hinge joints of the knee
Fig. 8.4 Fig. 8.4 Fig. 8.4 Fig. 8.4 Fig. 8.4 A pivotal joint
Pivotal joint
2020-21
Page 5


66 SCIENCE
8
Body Movements
S
it absolutely still. Observe the
movements taking place in your
body. You must be blinking your
eyes, time to time. Observe the
movements in your body as you
breathe. There are so many movements
that happen in our bodies.
When you are writing in your
notebook which part of the body are you
moving? Or, when you turn and look at
your friend? Different parts of your body
move while you remain at the same
place, in these examples. You also move
from one place to another — you get up
and go to your teacher or to the school
compound, or go home after school. You
walk, run, skip, jump and move from
place to place.
Let us see how animals move from
place to place by filling up Table 8.1,
after discussing with our friends,
teachers and parents.
Walk, run, fly, jump, creep, crawl,
slither and swim – these are only a few
of the ways in which animals move from
one place to another. Why are there so
many differences in the way that
animals move from place to place? Why
is it that many animals walk while a
snake slithers or crawls and a fish
swims?
8.1 HUMAN BODY AND ITS MOVEMENTS
Let us look closely at some of our own
movements to begin with, before looking
at all these varieties of movements in
animals.
Do you enjoy doing physical exercise
at school? How do you move your hands
and legs while doing different exercises?
Table 8.1 How do animals move
from place to place?
l a m i n A
d e s u t r a p y d o B
g n i v o m r o f
o t e c a l p m o r f
e c a l p
s e o d w o H
l a m i n a e h t
? e v o m
w o C s g e L k l a W
s n a m u H
e k a n S y d o b e l o h W r e h t i l S
d r i B
t c e s n I
h s i F
Boojho wonders about movements
in plants. He knows they do not
move from place to place, but, do
they show any other kind of
movements?
2020-21
67 BODY MOVEMENTS
Let us try some of the many movements,
our body is capable of.
Bowl an imaginary ball at an
imaginary wicket. How did you move
your arm? Did you rotate it at the
shoulder in a circular movement? Did
your shoulder also move? Lie down and
rotate your leg at the hip. Bend your
arm at the elbow and the leg at the knee.
Stretch your arm sideways. Bend your
arm to touch your shoulder with your
fingers. Which part of your arm did you
bend? Straighten your arm and try to
bend it downwards. Are you able to
do it?
Try to move the various parts of your
body and record their movements in
Table 8.2.
Why is it that we are able to move a
few parts of our body easily in various
directions and some only in one
direction? Why are we unable to move
some parts at all?
Activity 1
Place a scale length-wise on your arm
so that your elbow is in the centre
(Fig. 8.1).
Ask your friend to tie the scale and
your arm together. Now,
try to bend your elbow.
Are you able to do it?
Table 8.2 Movements in our body
s e t a t o R
y l e t e l p m o c
s e t a t o R
s n r u t / y l t r a p
s d n e B s t f i L
t o n s e o D
l l a t a e v o m
k c e N s e Y
t s i r W
r e g n i F
e e n K
e l k n A
e o T
k c a B
d a e H
w o b l E
m r A s e Y
Fig. 8.1 Can you bend your
arm now?
Body Part
Movement
2020-21
68 SCIENCE
Did you notice that we are able to bend
or rotate our body in places where two
parts of our body seem to be joined
together — like elbow, shoulder or neck?
These places are called joints. Can you
name more such joints? If our body has
no joints, do you think it would be
possible for us to move in any way at all?
What exactly is joined together at
these joints?
Press your fingers against the top of
your head, face, neck, nose, ear, back of
the shoulder, hands and legs including
the fingers and toes.
Do you get a feel of something hard
pressing against your fingers?  The hard
structures are the bones. Repeat this
activity on other parts of your body. So
many bones!
Bones cannot be bent. So, how do
we bend our elbow? It is not one long
bone from the upper arm to our wrist. It
is different bones joined together at the
elbow. Similarly, there are many bones
present in each part of the body.  We
can bend or move our body only at those
points where bones meet.
There are different types of joints in
our body to help us carry out different
movements and activities. Let us learn
about some of them.
Ball and socket joints
Activity 2
Roll a strip of paper into a cylinder. Make
a small hole in an old rubber or plastic
ball (under supervision) and push the
paper cylinder into it as shown in
Fig. 8.2. You can also stick the cylinder
on the ball. Put the ball in a small bowl.
Does the ball rotate freely inside the bowl?
Does the paper cylinder also rotate?
Now, imagine that the paper cylinder
is your arm and the ball is its end. The
bowl is like the part of the shoulder to
which your arm is joined. The rounded
end of one bone fits into the cavity
(hollow space) of the other bone
(Fig.8.3). Such a joint allows movements
in all directions.  Can you name another
such joint you can think of, recollecting
the body movements we tried at the
beginning of this section?
Pivotal Joint
The joint where our neck joins the head
is a pivotal joint (Fig. 8.4). It allows us
to bend our head forward and backward
and turn the head to our right or left.
Try these movements. How are these
movements different from those of our
arm that can rotate a complete circle in
Fig. 8.3 A ball and socket joint
Thigh Bone
Hip Bone
Fig. 8.2 Making a ball and socket joint
Ball and
Socket Joint
Bowl
Ball
Paper Cylinder
2020-21
69 BODY MOVEMENTS
its ball and socket joint? In a pivotal
joint a cylindrical bone rotates in a ring.
Hinge joints
Open and close a door a few times.
Observe the hinges of the door carefully.
They allow the door to move back
and forth.
Activity 3
Let us look at the kind of movement
allowed by a hinge. Make a cylinder with
cardboard or thick chart paper, as
shown in Fig. 8.5. Attach a small pencil
to the cylinder by piercing the cylinder
at the centre, as shown. Make a hollow
half cylinder from cardboard such that
the rolled up cylinder can fit inside it
easily. The hollow half cylinder with the
rolled up cylinder sitting inside it, allows
movement like a hinge. Try to move the
rolled up cylinder. How does it move?
How is this movement different from
what we saw with our constructed ball
and socket joint? We saw this kind of
movement at the elbow in Activity 1.
What we have constructed in Fig. 8.5 is
different from a hinge, of course. But, it
illustrates the direction in which a hinge
allows movement. The elbow has a hinge
joint that allows only a back and forth
movement (Fig. 8.6). Can you think of
more examples of such joints?
Fixed joints
Some joints between bones in our head
are different from those we have
discussed so far. The bones cannot move
at these joints. Such joints are called
fixed joints. When you open your
mouth wide, you can move your lower
jaw away from your head, isn’t it? Try
to move your upper jaw, now. Are you
able to move it? There is a  joint between
the upper jaw and the rest of the head
which is a fixed joint.
We discussed only some of the joints
that connect parts of our body.
What gives the different parts of the
body their different shapes?
If you wanted  to make a doll, what
will you make first? Perhaps a
framework to give the doll shape before
making its outer structure, isn’t it? All
the bones in our body also form a
framework to give a shape to our body.
Fig. 8.5 Fig. 8.5 Fig. 8.5 Fig. 8.5 Fig. 8.5 Directions of movement allowed by a hinge
like joint
Fig. 8.6 Fig. 8.6 Fig. 8.6 Fig. 8.6 Fig. 8.6 Hinge joints of the knee
Fig. 8.4 Fig. 8.4 Fig. 8.4 Fig. 8.4 Fig. 8.4 A pivotal joint
Pivotal joint
2020-21
70 SCIENCE
Fig. 8.9 Bones of the hand
Bend your fingers. Are you able to
bend them at every joint? How many
bones does your middle finger have?
Feel the back of your palm. It seems to
have many bones, isn’t it (Fig. 8.9)? Is
your wrist flexible? It is made up of
several small bones called carples. What
will happen if it has only one bone?
This framework is
called the skeleton
(Fig. 8.7.)
How do we know
that this is the shape
of a human skeleton?
How do we know the
shapes of the different
bones in our body? We
can have some idea
about the shape and
number of bones in
some parts of our body
by feeling them. One
way we could know
this shape better
would be to look at X-
ray images of the
human body.
Did you or anyone in your family
ever have an X-ray of any part of your
body taken? Sometimes when we are
hurt, or have an accident, doctors use
these X-ray images to find out about
any possible injuries that might
have happened to the bones. The X-
rays show the shapes of the bones in
our bodies.
 Feel the bones in your forearm,
upper arm, lower leg and upper leg. Try
to find the number of bones in each part.
Similarly, feel the bones of your ankle
and knee joints and compare these with
the X-ray images (Fig. 8.8).
The human skeleton is composed of
around 305 bones at birth. The
number of bones in the skeleton
changes with age. It decreases to 206
bones by adulthood after some bones
have fused together.
Fig 8.8 X-ray images of ankle and knee joints
Fig. 8.7 The
Human skeleton
Activity 4
Take a deep breath and hold it for a
little while. Feel your chest bones and the
back bone by gently pressing the middle
of the chest and back at the same time.
Count as many ribs (bones of the chest)
2020-21
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