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CBSE Class 5 Science Our Skeletal System

  • Our body consists of various organs like hands, legs, heart, lungs etc.

  • Each organ performs some specific functions.

  • All the organs work with perfect coordination and work like a wonderful machine to the body alive.

  • Bones and muscles together work like a team with efficiency and perfect coordination.

  • Bones and muscles together help in the movement of the body and the body parts.

  • A group of organs that together perform the same function make an organ system. E.g. digestive system, nervous system, respiratory system etc.

Skeletal System

  • Human skeleton is a framework of bones.

  • An adult human body has 206 bones of different shapes and sizes.

  • Human skeleton consists of a skull, a backbone, ribcage and two pairs of limbs.

  • The two pairs of limbs (forelimbs and hindlimbs) are attached to two pairs of girdles - the hip girdle and the should girdle.

The Skull

  • It is made of 22 bones.

  • 8 flat bones that are interlocked and enclose the delicate brain.

  • 14 facial bones. Only 2 facial bones are movable and enable us to talk and eat.

The Backbone

  • Skull is attached to the backbone which forms the main axis of the skeleton.

  • Backbone consists of 33 small ring-like bones called vertebrae which together form the vertebral column.


  • It consists of 12 pairs of bow-shaped rib bones that enclose the delicate heart.

  • Rib bones are joined to the backbone in the back and to the breastbone in the front.

  • The two pairs lowest rib bones are joined only to the backbone and are called floating bones.


  • The forelimbs i.e. arms are joined to the backbone with the help of shoulder girdles.

  • Shoulder girdles consist of a pair of shoulder blades and a pair of collar bones.

  • The hindlimbs i.e. legs are made of a strong thigh bone called the femur.

  • Femur is the longest bone in our bondy and bears the weight of the body.

  • Femur fits into the hip girdle with a ball and socket joint and is connected to the lower leg at the knee joint.

  • The long bones of the skeleton are hollow and are filled with a soft, fatty substance called the bone marrow which produces blood cells.

Functions of the skeleton

  • Gives shape, support and and strength to the body.

  • Protects the delicate internal organs.

  • Skull protects the delicate brain and the eyeballs rest inside the eye sockets.

  • Backbone protects the spinal cord.

  • Ribcage protects the heart and lungs.

  • Urinary bladder lies inside the hip girdles.

  • Muscles are attached to the bones and help in the movement of the body and body parts.

  • The enamel coating on the teeth is the hardest substance in the body.


  • A joint is the meeting point of two bones.

  • Two bones join together by a strong tissue called ligament.

  • There are many joints in the body.

  • All the joints except the joints in the skull are movable.

  • The bones in the skull are interlocked making the joints immovable.

  • There are two types of joints in the body - (i) Movable joints and (ii) Immovable joints.

Movable Joints:

The joints that can move. The bones at the joints move smoothly because of a fluid which acts like a lubricant.
There are 4 types of movable joints in our body. These are:
  1. Hinge joint
  2. Ball and socket joint
  3. Pivot joint
  4. Gliding joint

Hinge Joint

  • These joints are like the hinge of a door.

  • It can move the joint only in on direction.

  • Joints in our elbow, knee, fingers and toes are hinge joints.

Ball and Socket Joint

  • In this type of joint one bone has a rounded ball-like end on side that fits into the socket and allows maximum movement.

  • This joint is found at the hip and shoulder region.

Pivot Joint

  • The skull is joined to the first two vertebrae of the vertebral column with pivot joint.

  • The uppermost vertebra is called the atlas.

  • This joint allows our head to move in four directions i.e. sideways, up and down.

Gliding Joint

  • This joint allows the movement between two vertebrae of the vertebral column.

  • It allows our back to bend, twist and turn at each joint.

  • It also allows the movement at the wrist and ankle.

Muscles and Movement

  • The body muscles contract i.e. tighten up and relax (stretch) to produce movement of the body and body parts.

  • There are about 650 muscles in our body. Each muscle causes a particular movement.
  • Muscles bend our arms and knees, push food into the digestive canal, allow us to inhale air into the lungs, help us to chew food and make our heart beat.

  • Muscles are attached to the bones with strong fibres called tendons. These fibres become strong with regular exercise.

Types of Muscles

There are 3 types of muscles: (i) Voluntary muscles, (ii) Involuntary muscles and (iii) Cardiac muscles.
  1. Voluntary Muscles: Muscles that are under our control. We can move them out of our will.

  2. Involuntary Muscles: Muscles that are not under our control. These muscles control the actions of alimentary canal, movement of eye muscles etc.

  3. Cardiac Muscles: Muscles that are found only in the heart. These muscles are involuntary in function but their structure is like voluntary muscles.

How do muscles work?

  • Muscles produce movement in the body by pulling on the bones.

  • When the muscles contract, the bones come close to each other.
  • When we bend our knee, one muscle contracts and gets shorter, while the other muscles relax.

  • When we stretch our leg, the reverse happens.

  • Well developed muscles give a graceful appearance to the body.

  • To keep the muscles in good shape, we must maintain proper posture while sitting, standing and walking.

  • We must maintain good health by doing regular exercise and giving proper rest to the body.

  • We must eat healthy diet and avoid junk food.


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