Body Movements

8. Body Movements

Introduction: Sit absolutely still. Observe the movements taking place in your body. You must be blinking your eyes. There are movements in your body as you breathe. Animals walk, run, fly, jump, creep, crawl, slither and swim to move from one place to another.

Human Body and its Movements

We are able to bend or rotate our body in places where two parts of our body seem to be joined together. These places are called Joints.

Types of Joints:

• Ball and Socket Joint: The rounded end of one bone fits into the cavity (hollow space) of the other bone. Allows movement in all directions. (e.g., Shoulder, Hip).
• Pivotal Joint: The joint where our neck joins the head. Allows bending head forward/backward and turning right/left.
• Hinge Joint: Allows movement only in one plane (like a door hinge). (e.g., Elbow, Knee, Fingers).
• Fixed Joints: Bones cannot move at these joints. (e.g., Bones in skull - Upper jaw).

The Skeleton

The framework of bones that gives shape to our body is called the Skeleton. It consists of:

• Ribcage: Joins the chest bone and backbone together. Protects heart and lungs.
• Backbone: Made of many small bones called vertebrae.
• Shoulder Bones & Pelvic Bones: Pelvic bones enclose the portion of body below stomach.
• Skull: Protects the brain.

Cartilage: Parts of the skeleton that are not as hard as bones and can be bent. (e.g., Ear lobe, parts of nose).

Muscles: Muscles work in pairs. When one contracts, the bone is pulled. The other muscle relaxes. To move the bone in opposite direction, the relaxed muscle contracts.

Gait of Animals

Earthworm: Body made of rings joined end to end. No bones. Moves by alternate extension and contraction of body using muscles. Tiny bristles help in grip.

Snail: Moves with the help of a muscular foot. Carries a shell (outer skeleton) which is dragged along.

Cockroach: Has an outer skeleton. Three pairs of legs for walking. Two pairs of wings for flying.

Birds: Hollow and light bones. Forelimbs modified into wings. Shoulder bones are strong. Breastbones modify to hold flight muscles.

Fish: Streamlined body shape. Muscles make the front part curve to one side and tail to other, then quickly reverse, pushing body forward.

Snakes: Long backbone, thin muscles. Moves in loops. Each loop gives a forward push (Slithering).

Chapter Summary

• Bones and cartilage form the skeleton of the human body.
• The skeleton gives the frame and shape to the body and helps in movement. It protects the inner organs.
• The joint of the nature of hinge joint is found in the elbow and knee.
• The ball and socket joint is seen in the shoulder and hip.
• The movement is caused by the contraction and relaxation of muscles.
• Earthworms move by alternate extension and contraction of the body using muscles.
• Snails move with the help of a muscular foot.
• Snakes slither on the ground by looping sideways.

Exercise Q1: Fill in the blanks

• Joints of the bones help in the Movement of the body.
• A combination of bones and cartilages forms the Skeleton of the body.
• The bones at the elbow are joined by a Hinge joint.
• The contraction of the Muscle pulls the bones during movement.

Exercise Q2: True or False

• The movement and locomotion of all animals is exactly the same. (False)
• The cartilages are harder than bones. (False)
• The finger bones do not have joints. (False)
• The fore arm has two bones. (True)
• Cockroaches have an outer skeleton. (True)

Exercise Q3: Match the items

Exercise Q4: Answer the following

Q: What is a ball and socket joint?

Q: Which of the skull bones are movable?

Q: Why can our elbow not move backwards?

Key Facts and Definitions