Textbook: Our Skeletal System and the Skin | General Science Class 6 (Maharashtra Board) PDF Download

 Page 1


57
Sometimes when we fall while 
playing or have an accident, a bone in 
our arm or leg may get broken. This is 
called a ‘fracture’ of the bone.
A fracture in a bone causes severe 
and unbearable pain and the part with the 
broken bone swells immediately.
Your friend meets with an accident and 
a bone in his leg is fractured. How will 
you help ?
8.2 : A boy with a fractured bone
After an accident, prevent any movement of the fractured part. Immobilize it and 
get immediate medical help. After going to the hospital, an ‘X-ray’ image is taken of 
the part which is swollen.
‘X-rays’ were discovered by Wilhelm Conrad Roentgen.
In the previous 
classes, we have learnt 
about some organ systems, 
their functions and their 
locations in our body. With 
the help of that, complete 
the following table.
Which organ systems 
do you see in the figure 
alongside ?
The various organs are safe 
within the body cavity. The 
human skeleton is a protective 
shell for all the internal organs.
8.1 : Organ systems and the human skeleton
8.
Our Skeletal System and the Skin
Can you recall ?
Can you tell ?    
Name of 
the organ
Function of 
the organ
Body 
cavity
Heart
Lungs
Intestines
Brain
Page 2


57
Sometimes when we fall while 
playing or have an accident, a bone in 
our arm or leg may get broken. This is 
called a ‘fracture’ of the bone.
A fracture in a bone causes severe 
and unbearable pain and the part with the 
broken bone swells immediately.
Your friend meets with an accident and 
a bone in his leg is fractured. How will 
you help ?
8.2 : A boy with a fractured bone
After an accident, prevent any movement of the fractured part. Immobilize it and 
get immediate medical help. After going to the hospital, an ‘X-ray’ image is taken of 
the part which is swollen.
‘X-rays’ were discovered by Wilhelm Conrad Roentgen.
In the previous 
classes, we have learnt 
about some organ systems, 
their functions and their 
locations in our body. With 
the help of that, complete 
the following table.
Which organ systems 
do you see in the figure 
alongside ?
The various organs are safe 
within the body cavity. The 
human skeleton is a protective 
shell for all the internal organs.
8.1 : Organ systems and the human skeleton
8.
Our Skeletal System and the Skin
Can you recall ?
Can you tell ?    
Name of 
the organ
Function of 
the organ
Body 
cavity
Heart
Lungs
Intestines
Brain
58
Let’s identify our bones.
 (1) Place your hand at the centre of 
your chest and your friend’s back. 
 (2) What is the name of the hard part 
you feel on placing your hand on 
your chest ?
 (3) Do you feel some hard bumps on 
the back ? What are they called ?
 (4) What difference do you notice 
between the bones of the back and 
those of the chest ?
An X-ray image shows whether a bone is broken 
and also the exact spot where it is broken. This helps in 
providing the proper treatment.
8.3 : An X-ray image
The human skeletal system 
All the bones in our body are not of 
the same shape. Every bone is different. 
All the bones together form a framework 
or skeleton. The skeleton gives a shape 
to the body. 
All the bones of the body along 
with cartilage together form the skeletal 
system.
Bones are hard. They are not flexible. 
Bones are composed of two main 
constituents. Bone cells are biotic, while 
calcium carbonate, calcium phosphate, 
minerals and salts are the abiotic 
constituents of bones. Calcium imparts 
strength to the bones.
The system which gives a definite shape to the body, provides support and 
protects the delicate organs inside the body is the skeletal system.
Let’s try this.
2. Small bones  
3. Irregular bones
4. Long bones
Types of Bones : Bones of our body 
are classified into four types. 
1. Flat bones  
A fractured 
bone
Plaster
Page 3


57
Sometimes when we fall while 
playing or have an accident, a bone in 
our arm or leg may get broken. This is 
called a ‘fracture’ of the bone.
A fracture in a bone causes severe 
and unbearable pain and the part with the 
broken bone swells immediately.
Your friend meets with an accident and 
a bone in his leg is fractured. How will 
you help ?
8.2 : A boy with a fractured bone
After an accident, prevent any movement of the fractured part. Immobilize it and 
get immediate medical help. After going to the hospital, an ‘X-ray’ image is taken of 
the part which is swollen.
‘X-rays’ were discovered by Wilhelm Conrad Roentgen.
In the previous 
classes, we have learnt 
about some organ systems, 
their functions and their 
locations in our body. With 
the help of that, complete 
the following table.
Which organ systems 
do you see in the figure 
alongside ?
The various organs are safe 
within the body cavity. The 
human skeleton is a protective 
shell for all the internal organs.
8.1 : Organ systems and the human skeleton
8.
Our Skeletal System and the Skin
Can you recall ?
Can you tell ?    
Name of 
the organ
Function of 
the organ
Body 
cavity
Heart
Lungs
Intestines
Brain
58
Let’s identify our bones.
 (1) Place your hand at the centre of 
your chest and your friend’s back. 
 (2) What is the name of the hard part 
you feel on placing your hand on 
your chest ?
 (3) Do you feel some hard bumps on 
the back ? What are they called ?
 (4) What difference do you notice 
between the bones of the back and 
those of the chest ?
An X-ray image shows whether a bone is broken 
and also the exact spot where it is broken. This helps in 
providing the proper treatment.
8.3 : An X-ray image
The human skeletal system 
All the bones in our body are not of 
the same shape. Every bone is different. 
All the bones together form a framework 
or skeleton. The skeleton gives a shape 
to the body. 
All the bones of the body along 
with cartilage together form the skeletal 
system.
Bones are hard. They are not flexible. 
Bones are composed of two main 
constituents. Bone cells are biotic, while 
calcium carbonate, calcium phosphate, 
minerals and salts are the abiotic 
constituents of bones. Calcium imparts 
strength to the bones.
The system which gives a definite shape to the body, provides support and 
protects the delicate organs inside the body is the skeletal system.
Let’s try this.
2. Small bones  
3. Irregular bones
4. Long bones
Types of Bones : Bones of our body 
are classified into four types. 
1. Flat bones  
A fractured 
bone
Plaster
59
Can you identify the animals from the pictures of their 
skeletons ?
8.4 : Skeletons of various animals
Take a measuring tape and measure the 
length of the bones of your arms and 
legs. Do the same for your friend/ sister/
brother. Record the measurements in the 
table below and compare them.
The human skeletal system can be 
divided into two parts : the axial skeleton 
and the appendicular skeleton.
The axial skeleton consists of the 
skull, the spine and the rib cage. These 
are situated symmetrically along the 
central vertical axis of the body. 
The appendicular skeleton is made 
up of the bones of the upper and lower 
limbs (arms and legs) on either side of 
the central axis.  
Skull
8.5 : Parts of the human skeletal system
Can you tell ?    
Try this.
  Bones
Length of bones in cm.
Self  Friend Brother Sister  
1. Arm 
    bones
2. Leg
    bones
Rib cage
Arm
Spine
Leg 
Page 4


57
Sometimes when we fall while 
playing or have an accident, a bone in 
our arm or leg may get broken. This is 
called a ‘fracture’ of the bone.
A fracture in a bone causes severe 
and unbearable pain and the part with the 
broken bone swells immediately.
Your friend meets with an accident and 
a bone in his leg is fractured. How will 
you help ?
8.2 : A boy with a fractured bone
After an accident, prevent any movement of the fractured part. Immobilize it and 
get immediate medical help. After going to the hospital, an ‘X-ray’ image is taken of 
the part which is swollen.
‘X-rays’ were discovered by Wilhelm Conrad Roentgen.
In the previous 
classes, we have learnt 
about some organ systems, 
their functions and their 
locations in our body. With 
the help of that, complete 
the following table.
Which organ systems 
do you see in the figure 
alongside ?
The various organs are safe 
within the body cavity. The 
human skeleton is a protective 
shell for all the internal organs.
8.1 : Organ systems and the human skeleton
8.
Our Skeletal System and the Skin
Can you recall ?
Can you tell ?    
Name of 
the organ
Function of 
the organ
Body 
cavity
Heart
Lungs
Intestines
Brain
58
Let’s identify our bones.
 (1) Place your hand at the centre of 
your chest and your friend’s back. 
 (2) What is the name of the hard part 
you feel on placing your hand on 
your chest ?
 (3) Do you feel some hard bumps on 
the back ? What are they called ?
 (4) What difference do you notice 
between the bones of the back and 
those of the chest ?
An X-ray image shows whether a bone is broken 
and also the exact spot where it is broken. This helps in 
providing the proper treatment.
8.3 : An X-ray image
The human skeletal system 
All the bones in our body are not of 
the same shape. Every bone is different. 
All the bones together form a framework 
or skeleton. The skeleton gives a shape 
to the body. 
All the bones of the body along 
with cartilage together form the skeletal 
system.
Bones are hard. They are not flexible. 
Bones are composed of two main 
constituents. Bone cells are biotic, while 
calcium carbonate, calcium phosphate, 
minerals and salts are the abiotic 
constituents of bones. Calcium imparts 
strength to the bones.
The system which gives a definite shape to the body, provides support and 
protects the delicate organs inside the body is the skeletal system.
Let’s try this.
2. Small bones  
3. Irregular bones
4. Long bones
Types of Bones : Bones of our body 
are classified into four types. 
1. Flat bones  
A fractured 
bone
Plaster
59
Can you identify the animals from the pictures of their 
skeletons ?
8.4 : Skeletons of various animals
Take a measuring tape and measure the 
length of the bones of your arms and 
legs. Do the same for your friend/ sister/
brother. Record the measurements in the 
table below and compare them.
The human skeletal system can be 
divided into two parts : the axial skeleton 
and the appendicular skeleton.
The axial skeleton consists of the 
skull, the spine and the rib cage. These 
are situated symmetrically along the 
central vertical axis of the body. 
The appendicular skeleton is made 
up of the bones of the upper and lower 
limbs (arms and legs) on either side of 
the central axis.  
Skull
8.5 : Parts of the human skeletal system
Can you tell ?    
Try this.
  Bones
Length of bones in cm.
Self  Friend Brother Sister  
1. Arm 
    bones
2. Leg
    bones
Rib cage
Arm
Spine
Leg 
60
8.6 : Skull, rib cage and spinal column
The axial skeleton
Skull : The skull is formed by the bones of the head 
and face. The bones of the skull are flat and strong. There 
are altogether 22 bones in the skull, 8 in the head and 14 
in the face. Except for the lower jaw, none of the bones 
of the skull can move.
Which organs of our body does the skull protect ?
Rib cage : Feel the left and right sides of your chest 
with your hand or finger. How many bones can you feel 
altogether on the two sides ?
Check in the centre. How many bones do you feel ?
The cage-like structure in the chest is calld the rib 
cage. In the chest, there is one vertical, flat bone called 
the sternum. Twelve pairs of flat bones called ribs are 
joined to it sideways. These 25 bones form the rib cage. 
It is joined to the spine at the back.
The Spine (Backbone or Vertebral Column) : The 
spine is formed by padlock-shaped bones placed straight 
one above the other. There are altogether 33 bones in the 
spine, each called a vertebra. These bones are arranged 
one above the other flexibly. The spine protects the spinal 
cord that originates from the brain.
What would have happened if we didn’t have a 
backbone ?
Skull/
Cranium
The appendicular skeleton
The human body has two arms and two legs. The 
different parts of the arms and legs have several bones, 
which are connected together by joints.
As our body grows, the size and length of our bones increases. Such changes 
in size and length can be seen in children according to age. However, the body 
continues to grow only up to a certain limit. The bones of taller people are longer.
Do you know ?
There are three bones in each of the ears. 
Of these, the stirrup is the smallest bone in our 
body. It is as small as a grain of rice and is 
hollow. Its shape is like that of a stirrup.
In the human body, the longest and strongest 
bone is the thigh bone or the femur.
Stirrup
Lower jaw/
Mandible
Rib cage
Vertebrae
Back bone/
Vertebral 
column
Page 5


57
Sometimes when we fall while 
playing or have an accident, a bone in 
our arm or leg may get broken. This is 
called a ‘fracture’ of the bone.
A fracture in a bone causes severe 
and unbearable pain and the part with the 
broken bone swells immediately.
Your friend meets with an accident and 
a bone in his leg is fractured. How will 
you help ?
8.2 : A boy with a fractured bone
After an accident, prevent any movement of the fractured part. Immobilize it and 
get immediate medical help. After going to the hospital, an ‘X-ray’ image is taken of 
the part which is swollen.
‘X-rays’ were discovered by Wilhelm Conrad Roentgen.
In the previous 
classes, we have learnt 
about some organ systems, 
their functions and their 
locations in our body. With 
the help of that, complete 
the following table.
Which organ systems 
do you see in the figure 
alongside ?
The various organs are safe 
within the body cavity. The 
human skeleton is a protective 
shell for all the internal organs.
8.1 : Organ systems and the human skeleton
8.
Our Skeletal System and the Skin
Can you recall ?
Can you tell ?    
Name of 
the organ
Function of 
the organ
Body 
cavity
Heart
Lungs
Intestines
Brain
58
Let’s identify our bones.
 (1) Place your hand at the centre of 
your chest and your friend’s back. 
 (2) What is the name of the hard part 
you feel on placing your hand on 
your chest ?
 (3) Do you feel some hard bumps on 
the back ? What are they called ?
 (4) What difference do you notice 
between the bones of the back and 
those of the chest ?
An X-ray image shows whether a bone is broken 
and also the exact spot where it is broken. This helps in 
providing the proper treatment.
8.3 : An X-ray image
The human skeletal system 
All the bones in our body are not of 
the same shape. Every bone is different. 
All the bones together form a framework 
or skeleton. The skeleton gives a shape 
to the body. 
All the bones of the body along 
with cartilage together form the skeletal 
system.
Bones are hard. They are not flexible. 
Bones are composed of two main 
constituents. Bone cells are biotic, while 
calcium carbonate, calcium phosphate, 
minerals and salts are the abiotic 
constituents of bones. Calcium imparts 
strength to the bones.
The system which gives a definite shape to the body, provides support and 
protects the delicate organs inside the body is the skeletal system.
Let’s try this.
2. Small bones  
3. Irregular bones
4. Long bones
Types of Bones : Bones of our body 
are classified into four types. 
1. Flat bones  
A fractured 
bone
Plaster
59
Can you identify the animals from the pictures of their 
skeletons ?
8.4 : Skeletons of various animals
Take a measuring tape and measure the 
length of the bones of your arms and 
legs. Do the same for your friend/ sister/
brother. Record the measurements in the 
table below and compare them.
The human skeletal system can be 
divided into two parts : the axial skeleton 
and the appendicular skeleton.
The axial skeleton consists of the 
skull, the spine and the rib cage. These 
are situated symmetrically along the 
central vertical axis of the body. 
The appendicular skeleton is made 
up of the bones of the upper and lower 
limbs (arms and legs) on either side of 
the central axis.  
Skull
8.5 : Parts of the human skeletal system
Can you tell ?    
Try this.
  Bones
Length of bones in cm.
Self  Friend Brother Sister  
1. Arm 
    bones
2. Leg
    bones
Rib cage
Arm
Spine
Leg 
60
8.6 : Skull, rib cage and spinal column
The axial skeleton
Skull : The skull is formed by the bones of the head 
and face. The bones of the skull are flat and strong. There 
are altogether 22 bones in the skull, 8 in the head and 14 
in the face. Except for the lower jaw, none of the bones 
of the skull can move.
Which organs of our body does the skull protect ?
Rib cage : Feel the left and right sides of your chest 
with your hand or finger. How many bones can you feel 
altogether on the two sides ?
Check in the centre. How many bones do you feel ?
The cage-like structure in the chest is calld the rib 
cage. In the chest, there is one vertical, flat bone called 
the sternum. Twelve pairs of flat bones called ribs are 
joined to it sideways. These 25 bones form the rib cage. 
It is joined to the spine at the back.
The Spine (Backbone or Vertebral Column) : The 
spine is formed by padlock-shaped bones placed straight 
one above the other. There are altogether 33 bones in the 
spine, each called a vertebra. These bones are arranged 
one above the other flexibly. The spine protects the spinal 
cord that originates from the brain.
What would have happened if we didn’t have a 
backbone ?
Skull/
Cranium
The appendicular skeleton
The human body has two arms and two legs. The 
different parts of the arms and legs have several bones, 
which are connected together by joints.
As our body grows, the size and length of our bones increases. Such changes 
in size and length can be seen in children according to age. However, the body 
continues to grow only up to a certain limit. The bones of taller people are longer.
Do you know ?
There are three bones in each of the ears. 
Of these, the stirrup is the smallest bone in our 
body. It is as small as a grain of rice and is 
hollow. Its shape is like that of a stirrup.
In the human body, the longest and strongest 
bone is the thigh bone or the femur.
Stirrup
Lower jaw/
Mandible
Rib cage
Vertebrae
Back bone/
Vertebral 
column
61
Observe a human skeleton in your school laboratory or a picture of the skeleton 
and classify the bones in our body into four types. Discuss the functions of these bones.
Move the different parts of your body 
from the head to the toes and observe the 
different places at which they can bend 
or turn.
The bones in our body are connected to 
each other by means of ligaments.
Types of joints
Let us study some types of movable 
joints.
1. Hinge joint : This type of joint 
allows the movements of bones only in 
one direction. It moves in a 180
0
 angle. 
Examples : the elbow and knee joints.
2. Ball and socket joint : In this 
type of joint, the bones can move in two 
or more directions - in a 360
0
 angle. 
Examples : shoulder and hip joints.
3. Gliding joint : In this type of 
joint, the bones can only slide over each 
other. Examples : wrist and ankle joints.
Gliding 
joint
Hinge joint
Ball and 
socket 
joint
8.7 : Some types of joints
Joints : Joints are the places 
where two or more than 
two bones are connected to each 
other. Joints are of two types.
Observe and discuss.
Movable Joint 
Bones can move.
Examples : bones 
of arms and legs
Immovable Joint
Bones cannot move.
Example : bones of 
the skull.
(Other than the lower 
jaw)
$ $
 Joints
Try this.