Class-6th SCIENCE

STUDY NOTES & WORKSHEET

BODY MOVEMENTS

BODY MOVEMENTS

1. SKELETON (Framework of Bones)

The ability of a human being (or an animal) to move its body from one place to another is called locomotion. Human beings show two types of body movements: Movements of the body parts (like mouth, head, backbone, arms,

hands, legs and foot, etc.), and Movement of the whole body from one place to another (which is

called locomotion).

The bony framework inside our body is called skeleton. In human beings, the skeleton is inside the body, so it is called an ‘endoskeleton’. Skeleton is called ‘kankal’ in Hindi.

The bones of skeleton provide a framework which holds our body together. The skeleton also gives a shape to our body. The human skeleton is made mostly of bones with some cartilage in certain parts. Bones are hard and tough but cartilage is softer than bones. The skeleton is made of bones of many different shapes and sizes. The x-ray images show the shape and number of bones in the various parts of our body. There are 206 bones in the human skeleton. The bones of skeleton are interconnected through joints to form various parts of our body. Our skeleton has movable joints between various bones which allow the muscles to move the head, shoulders, arms, legs, and other parts of the body.

1.1 Description of Skeleton

The skeleton consists of : Skull, Backbone, Ribs, Breastbone, Shoulder bones, Hip bone, Arm bones and Leg bones. The human skeleton consists of a strong backbone which has skull at its top end. The skull has eye

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sockets, an upper jaw, and a lower jaw in it. Ribs are attached to the upper part of backbone forming a rib cage. There is a breastbone called sternum in front of the rib cage. At the lower end of backbone is a wide and strong structure called hip bone. Just below the neck, there are shoulder bones on both the sides of the skeleton. The shoulder bones consist of two bones: Collar bone and shoulder blade. The scientific name of collar bone is clavicle and that of shoulder blade is scapula.

The upper limb of human body from the shoulder to the hand is called an arm. There are two arms in the human skeleton. The two arms are attached to the two shoulder blades of the skeleton by ball and socket joints. The upper arm consists of a single bone called humerus. The lower arm is from elbow to wrist. The lower arm is made up of two bones: Radius and ulna. The lower limbs of the body on which a person walks or stands are called legs. There are two legs in the human body. The two legs are attached to hip bone of the skeleton by ball and socket joints. The upper leg consists

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of a single bone called femur. Femur is commonly known as thigh bone. The lower leg is from knee to ankle. The lower leg consists of two bones: tibia and fibula. The foot consists of various types of small bones which form ankle, middle part of foot and toes.

1.2 Functions of Skeleton

The important functions of skeleton are as follows: (a) Skeleton holds the whole body together and gives it a shape. (b) Skeleton protects many delicate internal organs of the body from

outside damage. (c) Skeleton provides numerous points for the attachment of muscles of

the body. (d) Alongwith muscles, skeleton helps in the movement of body parts

and locomotion.

1.3 Skull

The bony part of our head is called skull. The skull is made of 22 bony plates joined together. Our brain is inside the skull in its upper part. The brain is made of soft tissue which could be easily damaged without a hard covering. The bones of skull form a strong case around the brain. In this way, skull protects the brain. The lower part of skull contains the face bones (including nose bone). Our face has sense organs like eyes, ears and nose.

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Some of the main functions of the skull are as follows: Skull protects the brain. Skull protects the sense organs of the face Skull gives shape to our head.

1.4 Backbone

The backbone is a long hollow, rod-like structure running from the neck to the hips, inside our body. The scientific name of backbone is vertebral column. Backbone forms the main supporting structure of the body (or skeleton). Backbone is made up of 33small bones placed one over the other. The small bones which make up the backbone are called vertebrae. Between the various vertebrae of backbone are the discs of cartilage (soft bones). These discs allow the vertebrae to move slightly and enable the backbone to bend forwards and backwards (or from side to side). Our backbone supports the head at its top. The shoulder bones, rib bones and hip bone are all joined to the backbone. Each vertebra has a hole in it. Due to this, there is a hollow centre inside the backbone. The spinal cord passes inside the hollow cavity of the backbone. Thus, backbone encloses and protects the spinal cord from damage.

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The main functions of backbone are as follows: (a) Backbone provides main support to the body. (b) Backbone supports the head at its top. (c) Backbone attaches shoulder bones, ribs and hip bone. (d) Backbone protects the spinal cord.

1.5 Rib Cage

Ribs are the curved bones in our chest. Ribs exist in pairs. There are 12 pairs of ribs in the chest of our body. The hollow bony structure formed by the ribs is called ‘rib cage’. Some of the important internal organs of our body such as heart, lungs and liver lie inside the strong bony rib cage. The rib cage protects the delicate internal organs like heart, lungs and liver. The rib cage also takes part in our breathing movements.

The main functions of the rib cage are the following:

Rib cage protects the internal organs of the body such as heart, lungs and liver.

Rib cage takes part in our breathing movements.

1.6 Shoulder Bones

Shoulders are that part of the body to which our arms are attached. The human body has two shoulders, one on each side of the neck. There are two shoulder bones: collar bone and shoulder blade. The collar bone is a

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long, curved bone. Collar bone keeps the shoulders apart. The shoulder blade is a large and flat triangular bone. The upper arm fits into the socket of shoulder blade forming ball and socket joint. The main functions of the shoulder bones are the following:

(a) Collar bones on the two sides of the neck keep our shoulders apart.

(b) Shoulder blades attach the arms to our body. (c) Shoulder blades provide sites for muscle attachments which move

the arms, neck and upper part of our body.

1.7 Hip Bone (Pelvic Bone)

The hip bone forms a large, basin-shaped frame at the lower end of the backbone, to which the legs are attached. The hip bone is also known as pelvic bone. Hip bone is not a single bone. It is made up of a number of

bones fused together by fixed joints. The hip bone encloses the portion of our body below the stomach. The thigh bones of our legs are joined to the hip bone by the ball and socket joints. Actually, hip bone forms the link between upper part of our body and the legs.

The important functions of the hip bone are as follows: (i) Hip bone supports and protects the lower organs of the body such as

intestines, urinary bladder and internal sex organs. (ii) Hip bone attaches the legs to our body. (iii) Hip bone provides sites for the attachment of muscles that move

legs, hips and trunk.

1.8 Bones of the Hand

Our hand is made up of three parts: wrist, palm and fingers. The wrist consists of 8 small bones known as carpals. The wrist

bones form movable joint with the bones of forearm. The palm of hand is composed of 5 longer bones called metacarpals.

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The fingers are made of jointed bones called phalanges. There are 3 bones in each finger but the thumb has only 2 bones.

1.9 Cartilage

Most of the skeleton consists of hard bones. However, at some places in the skeleton there is a material which is not as hard as bones and which can be bent. It is called cartilage. Cartilage is a firm but flexible material found at some places in the skeleton. Cartilage is much softer than bone. Cartilage can be bent without breaking. In fact, cartilage is a kind of softer and elastic bone. Cartilage is present in the following places in our body:

(a) Cartilage is present in the pinnae of ears. (b) Cartilage is found at the end of nose. (c) Cartilage is found on the end of bones where they meet one another

at a joint. (d) Cartilage is also present between the vertebrae of backbone.

Upper part of ear has cartilage The ear lobe The upper part of our ear is called pinna and the lower part is called ear lobe. Cartilage gives support and shape to the ear. Cartilage is flexible that is why we can bend the pinna of our ear quite freely, without the danger of breaking. It is the presence of cartilage which gives support and shape to our nose and ears. Cartilage is also found on the ends of bones where they meet one another at a joint. Cartilage is smooth. The layer of smooth cartilage reduces friction and allows the ends of bones to move easily over each other without damaging them. The presence of cartilage discs between vertebrae makes the backbone flexible, so that it can bend. The cartilage discs also absorb the shocks when we run, jump or do other such activities.

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2. JOINTS of the BODY

Our skeleton is made up of hard and strong bones. Bones cannot be bent. We can bend our body parts only at those places where two or more bones join together. Such places are called joints. The place where two or more bones meet in the skeleton is called a joint. Several types of joints occur in the human skeleton. Joints of the bones help in body movements. We can move our head, arms, hands, legs, and feet because all these parts have ‘bone joints’. In the freely movable joints, the ends of bones forming the joint are held in place by strong connective tissue called ‘ligaments’. Ligaments connect the bones forming the joints and prevent the bones from falling apart during movement. The ends of the bones at joints are covered with a soft and smooth layer of cartilage. The layers of cartilage allow the ends of the bones to move over each other smoothly without friction. This prevents damage to the ends of bones due to wear and tear caused by rubbing over each other. There is also a thick oily liquid between the ends of bones of a freely movable joint.

3. TYPES of JOINTS

There are different types of joints in the human skeleton to help us to carry out different kinds of movements or other activities. The movability of joints vary depending on different factors. Joints have been classified into three major structural forms, namely, fibrous, cartilaginous and synovial.

Fibrous joints do not allow any movement. This type of joint is shown by the flat skull bones which fuse end-to-end with the help of dense fibrous connective tissues in the form of sutures, to form the cranium.

In cartilaginous joints, the bones involved are joined together with the help of cartilages. The joint between the adjacent vertebrae in the vertebral column is of this pattern and it permits limited movements.

Synovial joints are characterised by the presence of a fluid filled synovial cavity between the articulating surfaces of the two bones. Such an arrangement allows considerable movement. These joints help in locomotion and many other movements. Ball and socket joint (between humerus and pectoral girdle), hinge joint (knee joint), pivot

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joint (between atlas and axis), gliding joint (between the carpals) and saddle joint (between carpal and metacarpal) are some examples.

3.1 Hinge Joints

If we open and close a door, we will find that the door can move only ‘forwards’ and ‘backwards’. A door is said to have a hinge joint. In our body also, we have some bone joints which move like a door on its hinges. They are called hinge joints.

Directions of movement allowed Hinge joints of the knee

by a hinge like joint A hinge joint allows the movement of bones in only one direction: forwards and backwards. In a hinge joint, the movement of bones is restricted to one direction by the shape of the ends of the bones which form the joint, and by the ligaments which hold the bones together at the joint. Elbow, knee, knuckles (finger joints) and jaw are hinge joints.

3.2 Ball and Socket Joints

In the ball and socket joint, one end of the bone has a round shape like a ‘ball’ which fits into a ‘socket’ (hollow space) in the other bone. In the ball and socket joint, the bones can be turned in any direction: forwards and backwards, side to side, and even rotated.

Making a ball and socket joint A ball and socket joint

The shoulder joints and hip joints are ball and socket joints. A ball and socket joint allows much more movement of bones than a hinge joint.

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3.3 Pivot Joints

In a pivot joint, a cylindrical bone turns in a ring-type bone. The pivot joints allow rotation around an axis. A pivot joint exists between our skull and neck (or a pivot joint exists between our head and neck). A pivot joint connects our head to the neck. Another pivot joint occurs in the forearm (lower arm) near the elbow.

3.4 Fixed Joints

In some joints, the bones are held so tightly together that they cannot move at all. Such joints are called fixed joints. In fixed joints, the bones are held very firmly together by strong fibres. The fixed joints are immovable joints. The function of fixed joints is to provide strength and support to the body, or to protect delicate organs (like brain) which cannot withstand any kind of deformation. Fixed joints occur in our skull. The plate-type bones of our skull are held together by fixed joints and cannot move at all. This makes the skull very strong. The hard and strong skull protects a delicate organ of our body called ‘brain’. There is a fixed joint between the skull and the upper jaw. We can move the lower jaw because the lower jaw is connected to the skull by a movable joint called hinge joint. Fixed joints also occur in the hip bone.

4. MUSCLE CONTRACTIONS MOVE BONES AT JOINTS

Muscle is the fibrous tissue in the body that has the ability to contract (when asked to do so by the brain). When a muscle contracts, it shortens (becomes smaller). Muscles are attached to the bones of our skeleton (through strong fibres called tendons). So, when the muscle attached to a bone contracts, it pulls the bone due to which the bone moves at the joint. A muscle can only pull a bone, it cannot push a bone. The muscles joined to our bones (or skeletal muscles) work in pairs. When one muscle of the pair contracts (or shortens), then the other muscle of the pair is stretched (or relaxed).

The movement of body parts (and locomotion) in human beings is brought about by the alternate contraction and stretching of the muscles attached to the movable bones of the skeleton.

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4.1 Bending and Straightening of Arm

Our arm consists of two parts, upper arm and lower arm, which are joined at the elbow. The upper arm has one bone. The lower arm has two bones. The upper arm bone has a pair of muscles called ‘biceps’ and ‘triceps’ on its two sides. The upper end of both the muscles is attached to the fixed bone called shoulder blade by tendons.

When we want to bend the arm, the biceps muscle contracts. Biceps muscle is called flexor muscle because it flexes (bends) the arm. When biceps muscle contracts and bends the arm, the triceps muscle stretches or relaxes.

When we want to straighten the arm, the triceps muscle contracts (it becomes shorter and fatter). Triceps muscle is called extensor muscle because it straightens (extends) the arm. Two muscles work together to move a bone

5. MOVEMENT IN ANIMALS

It is necessary for the animals to be able to move from one place to another to find food and escape from their enemies. Human beings walk by contracting and relaxing muscles in their legs in a co-ordinated manner. Every animal has to push something ‘backwards’ with its body part to be able to move ‘forward’. For example, a fish pushes on water backwards with its tail to move forward. Cockroach and birds are the animals which have legs to walk on ground and wings to fly in air.

5.1 Cockroach

Cockroach is an insect. The body of a cockroach is covered with hard and tough outer covering called ‘exoskeleton’. The skeleton of cockroach is called exoskeleton because it is outside the body (‘exo’ means ‘outside’). The exoskeleton provides great protection to the internal organs of cockroach and also provides sites for the attachment of muscles. The

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cockroach moves on ground as well as flies in air. A cockroach has six legs (three legs on each side of its body). The cockroach moves on the ground by using its legs. The cockroach flies in air by moving its wings up and down rapidly with the help of flight muscles. When the wings of cockroach move down they push on air downward and backward. The downward push on air lifts the cockroach up into air, and the backward push on air makes it move forward.

5.2 Birds

Sparrow, crow, pigeon, eagle, hen, duck, swan, and peacock, are all birds. Birds walk on the ground and also fly in air. Some birds also swim in water. Birds walk on the ground by using their hind limbs. Those birds which swim in water do so by pushing against water with their hind limbs which have webbed feet.

The birds can fly because their bodies are adapted for this purpose. The main adaptations which have been made in the bodies of birds by nature to enable them to fly are the following: (a) Their forelimbs are modified to form wings for flying. (b) Their flight feathers provide a large

flat surface which is light but strong. (c) Their bones are hollow and light. (d) Their bodies are streamlined and

extremely light. (e) They have powerful flight muscles. (f) Their breastbone is extended for the

attachment of large flight muscles (which move the wings up and down).

Birds fly by a constant flapping (up and down movement) of their wings. During the downstroke, the raised wings of a bird go down and back. When the wings go down, they push the air down. During the downstroke of wings, the air is pushed downwards and backwards. The equal and opposite reaction force of air pushes the bird up and forward, and makes it fly.

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6. MOVEMENT WITHOUT LEGS

The animals which do not have legs use only the muscles of their body for moving from place to place. Some of the animals which do not have legs are earthworm, snail, fish and snake.

6.1 Earthworm

An earthworm does not have bones or legs. It has muscles which help to lengthen and shorten the body. An earthworm’s body consists of liquid-filled segments joined together. Normally, the segments of earthworm’s body are short and fat. The earthworm’s body has two types of muscles: circular muscles and longitudinal muscles.

(i) When circular muscles contract, they make the segments of earthworm’s body long and thin.

(ii) And when longitudinal muscles contract, they make the long and thin segments of earthworm’s body short and fat again.

An earthworm moves by ‘lengthening’ and ‘shortening’ its body alternately by using the circular muscles and longitudinal muscles, respectively. The tiny bristles on the underside of earthworm’s body help in gripping the ground when a part of its body moves.

6.2 Snail

Snail is a very slow moving animal with a shell on its back. The body of a snail is soft and consists of a head, a foot and a shell. The head of snail has two pairs of tentacles for catching prey. The larger pair of tentacles has little eyes in them. Shell is the outer skeleton of snail but it is not made of bones. Shell contains the internal organs of the snail. The snail has only one foot under its body. The foot of snail is large, flat and disc-shaped, which is made of strong muscles. It is called muscular foot. The snail moves with the help of a large, disc-shaped muscular foot. Snails are ‘gastropods’ which means ‘belly-footed animals’. The movement of snail is called ‘creeping’. Snail

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6.3 Fish

Fish can move in water because its body is specially adapted for this purpose. Fish is adapted to move in water by having a streamlined shape, flexible backbone, powerful body muscles and fins.

(a) The Fish has Streamlined Body. The body of fish tapers at both ends (being thin in front, thick in middle and again thin at the back). This body shape is called ‘streamlined’. Due to streamlined shape, water can easily flow around the body of fish and offers least resistance to the movement of fish.

(b) The Fish Has Flexible Backbone. Due to flexible back-bone, the fish can bend its body easily from side to side to move through water.

(c) The Fish Has Powerful Body Muscles. The powerful body muscles of the fish on both sides help in moving its tail on both sides.

(d) The Fish Has Fins. The thin and flat projections on the body of fish are called fins. The fins help the fish in steering, balancing and stopping in water. The tail fin also helps in moving the fish forward in water.

A fish swims in water by moving its tail from side to side. The side-to-side movements of tail are brought about by the alternate contractions and relaxation of muscles on the two sides of the body of fish. When the fish’s tail moves from side to side, it pushes the water sideways as well as back-wards. The backward push of tail on water makes the fish move forward.

Movement in Fish 6.4 Snake

The body of a snake is long and cylindrical. The snake has a long and flexible backbone which makes its body bend easily to form loops. It has also strong muscles connected to its skeleton. Snakes do not have legs, even then they move quite fast. Snakes use their whole, long and flexible body to move from one place to another.

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A snake ‘moves forward’ by moving its body ‘sideways’ in the form of many loops, and pushing against the ground (with the underside of moving loops). A snake contracts and relaxes the muscles on the two sides of its body alternately to form many loops in which different parts of the snake’s body are moving to the left side and right side at the same time. Each sideways moving loop of snake’s body pushes back against the ground and gives the snake a forward push. The special name of the wave-like motion of a snake is ‘slither’. The snakes slither on ground by looping sideways. A snake does not move in a straight line. This is because the sideways pushes of the loops push the snake forward as well as sideways.

6. DISORDERS OF MUSCULAR AND SKELETAL SYSTEM

Some of the common disorders of the muscular and skeleton system are briefly explained as follows:

Myasthenia gravis: Auto immune disorder affecting neuromuscular junction leading to fatigue, weakening and paralysis of skeletal muscle.

Muscular dystrophy: Progressive degeneration of skeletal muscle mostly due to genetic disorder.

Tetany: Rapid spasms (wild contractions) in muscle due to low Ca++ in body fluid.

Arthritis: Inflammation of joints. Osteoporosis: Age-related disorder characterised by decreased bone

mass and increased chances of fractures. Decreased levels of estrogen is a common cause.

Gout: Inflammation of joints due to accumulation of uric acid crystals.

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CLASS-6th (Science) Topic: Body Movements

WORKSHEET-1

1. What runs through the centre of backbone ? 2. What is the name of small bones which make up backbone ? 3. What is present between the various vertebrae of backbone ? 4. What are the curved bones present in our chest known as? 5. Name the material which gives support and shape to organs

like ears and nose. 6. Which parts of human body are protected by the following?

(a) Skull (b) Rib cage (c) Backbone 7. Which part of skeleton protects the following ?

(a) Brain (c) eyes (b) Heart and lungs (d) Spinal cord.

8. Write the main functions of skull. 9. What is a rib cage? State the function of rib cage. 10. Name two shoulder bones? Write the functions of shoulder

bone. 11. What is hip bone? Write its functions. 12. What is cartilage? Name some of our body parts where

cartilage is found. 13. What is skeleton? What are the various functions of skeleton? 14. What is backbone? What is the scientific name of backbone?

Write the main functions of backbone. 15. What are the various parts of our hand? Name the various

bones present in our hand. 16. A, B and C are some of the parts of human skeleton. Part A is

a long, hollow, rod like structure which encloses and protects the spinal cord. Part B is at the top end of part A and it protects the brain. Part C is at the lower end of part A and

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forms two ball and socket joints with thigh bones. What are A, B and C ?

17. There are 12 pairs of curved bones called X in our chest region. One end of bones X is joined to backbone and their other end is joined to bone Y in the front to form a box like structure Z. this strong box like structure protects the delicate internal organs P, Q and R of our body. (a) What are (i) X (ii) Y, and (iii) Z ? (b) Name the organs: (i) P (ii) Q (iii) R

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CLASS-6th (Science) Topic: Body Movements

WORKSHEET-2

1. What type of joint connects our head to neck ? 2. What types of joints are mainly present in the skull ? 3. Which of the two allows greater movement:

(a) A ball and socket joint, or (b) Hinge joint 4. What type of joint makes our head turn from side to side ? 5. Name an animal which moves by lengthening and shortening

its body segments alternately. 6. Name two places in our body where pivot joint occur. 7. A traffic policeman stretches his arm to the right. During this

movement: (a) Which of the muscle contracts? (b) Which of the muscle stretches (or relax)?

8. What type of joint occurs at (a) elbow and (b) knee ?

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9. What type of joint is (a) Shoulder joint (b) Hip joint ? 10. What type of joints exists between:

(a) Upper jaw and rest of skull ? (b) Lower jaw and rest of skull ?

11. What happens when (a) Your biceps muscle contracts ? (b) Your triceps muscle contracts ?

12. Give one example each of: (a) Fixed joint (c) ball and socket joint (b) Hinge joint (d) Pivot joint

13. Which material is present at the end of bones in a joint ? How does it help ?

14. Name two hinge joints and two ball and socket joints in our body. Where can you find fixed joints in the human skeleton?

15. What is a joint? Name four types of joints in human body. Draw a labelled diagram to show the elbow joint.

16. What type of joint is the ‘knee joint’ ? Describe it. 17. The hip bone has two hollow spaces called P whereas the

upper ends of the thigh bones are round in shape. At our hip, the upper ends of two thigh bones fit into empty spaces P to from joints Q. (a) What are the empty spaces P in hip bone known as ? (b) What type of joints are Q ? (c) How does joint Q differ from knee joint ?

18. How does the movement of body parts takes place in human beings ?

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CLASS-6th (Science) Topic: Body Movements

WORKSHEET-3

1. Name an animal which moves by using its large disc shaped muscular foot.

2. Name an animal which swims in water by moving its tail from side to side.

3. Name an animal which moves on ground by looping its body sideways.

4. Name two birds which can also swim in water. What kind of feet do they have?

5. How does a bird fly in air? 6. How does an earthworm move? 7. Describe the movement of snake and snail? 8. How does a bird walk on the ground? What are the various

ways in which birds are adapted for flying? 9. (a) How many legs does a cockroach have? How does a

cockroach move on the ground ? (b) How many wings does a cockroach have ? How does a cockroach fly in air ?

10. The animals A, B, C and D all move without legs. The animal A moves by the alternate contractions and relaxations of the muscles of its disc shaped foot. The animal B lives in water and swims by moving its tail from side to side. The animal C lives in soil and moves by lengthening and shortening its body segments alternately. The animal D moves forward by moving its body sideways in the form of many loops. What are A, B, C and D ?

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