User:Samikshajain/Sandbox

'CBSE' Class - 6 'Science'

=BODY MOVEMENTS=

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''Human beings exhibit locomotion. Locomotion is brought about by the combination of muscular and skeletal system. The bending and movement of the skeleton is brought about by special structures called as joints.''

JOINTS
''Joint is a point at which two separate bones meet. Joints are held at position by strong cords called as ligaments. Joints can be classified based on the type of movement they bring about. There are three main types of joints in the human body. They include fixed or immovable joints, slightly movable joints and freely movable joints.  a) Fixed or immovable joints are the joints which do not allow the structure to move but they offer protection for the structure in which they are present. Examples are the sutures between the bones of the cranium,ribs in the breast bone, bones of the hip girdle.

b) Slightly movable joints provide support to the structure in which they are present. They also help the structure to move slightly. Example includes joints of the lower jaw which are slightly movable.

c) Freely movable joints are the joints which solely help in the movement of the structure or organ in which they are present. Four immovable joints present in our body are Ball and socket joint, Pivot joint, hinge joint and the gliding joint. ''

Ball and Socket Joint
This joint is formed by two bones in which one end of a bone is rounded and ball-like. It fits into a cup-like depression of the other bone. This joint provides movement in any direction. Examples of a ball and socket joint are shoulder joints and hip joints.

Pivot Joint
This is the joint in which one bone fits into a ring formed by the other bone. It rotates over the pivot-like end of the other bone. Example is the joint which joins the neck to the head. Head rotates over the neck.

Hinge Joint
''This is a joint which moves like a hinge in a single plane not more than 180 degrees. It provides back and forth movement of the structure. This is a joint which can be compared to that of a hinge in the door. Examples of a hinge joint are the elbow joint and the knee joint.''

Gliding Joints
''This is a joint which allows bones to glide over each other. These types of joints provide little movement in all directions. These are the joints present at the ankles,wrist and between vertebrae. ''

Movement In Bones
Joints along with muscles can bring about movement in bones.

One end of the muscle is attached to a movable bone and the other end of the muscle is attached to a fixed bone.

Muscles are attached to bones by tough cords called as tendons.

Muscles work in pairs and bring about movement by contraction and relaxation.

The paired muscles are biceps and triceps which together help in the movement of the structures like arm, leg etc.

Contraction brings in the shortening of the muscle and relaxation brings about lengthening of the muscle.

It makes the muscle short, thick and stiff to pull the bone.

When the arm is folded, biceps contract and triceps relaxes and lengthens. When the arm is straightened, biceps relax and lengthen whereas triceps contract.

SKELETON
The framework of the body formed by the bones and cartilage.

Functions of Skeleton
1.The skeleton gives shape to our body. 2. Skeleton protects many delicate internal organs. 3. Skeleton provides numerous point for attachment of muscles.

DECRIPTION OF SKELETON
a. Skull The bony part of head is called skull. The skull is made up many bones joined together. It protects the brain.

b. Ribcage Ribs are curved bones in the body. There are 12 pairs of ribs. the ribs are curiously bent. They join the chest bone and the backbone together to form a box. This is called a ribcage. Ribcage protects the internal organs of the body like heart, lungs.

c. Backbone The backbone is a long hollow, rod like structure running from the neck to the hips. Backbone is made up of 33 small bones placed one over the other. These small bones are called vertebrae. It provides support to the body and protects spinal cord. d. pelvic bones The pelvic bones form a large, basin shaped frame at the lower end of the backbone , to which legs are attached. The pelvic bones encloses the portion of our body below the stomach.

MUSCLES
''Muscle is a fibrous tissue in the body which has ability to contract. When muscle contracts, it shortens it pulls the bone due to which the bone move at that joint. A muscle can only pull a bone it cannot push a bone. The muscles joined to our bones work in pairs. When one muscle of a pair contracts, then the other muscle of a pair is relaxed. A contracted muscle can come back to its original position only when the other muscle of the pair pulls it by contracting itself.''

Movement in Earthworm
''The body of earthworm is made up of many rings joined end to end. it has muscles which help to extend and shorten the body. Under its body it has large number of bristles which are connected with muscles. This bristles help to get grip on the ground. During movement, the earthworm first extends the front part of body , keeping the rear portion fixed to the ground. Then it fixes the front end and release the rear end. It then shortens the body and pull the rear end forward. This makes it forward by small distances. Repeating such muscle contraction and relaxations, the earthworm can move through soil. Its body secrete a slimy substance to help movement.''

Movement in Snail
''The body of snail consist of head, foot and shell. Shell is outer skeleton of the snail but it is not made up of bones .Shell contains internal organs of snail. In dangerous condition, the snail withdraw its head and foot in the shell. Snail foot is large, flat and disc shaped which is made up of strong muscles , muscular foot .The snail moves with the help of large disc shaped muscular foot. There are two sets of muscles in the foot of snail which contracts and expands alternatively producing a kind of wave effect. A series of wave in the muscle of the foot makes the snail move forward.''

Movement in cockroach
''Cockroach is an insect. the body of cockroach is covered with hard outer skeleton .this outer skeleton is made up of many units joined together and that permits movement. It has three pair of legs and two pairs of wings attached to the breast. The cockroach has distinct muscles near legs which help in walking while the breast muscles move the wings when the cockroach flies.''

Movement in Fish
''Fish is adapted to swim in water by having; The fish has a streamlined body shape which means head and tail of the fish are smaller than the middle portion of the body - the body tapers at both the ends. Due to the streamlined shape, water can easily flow around the body of fish and offers least resistance to body.Fish has a flexible backbone.The fish has powerful body muscle.The fish has fins. During movement, muscles make the front part of the body curve to one side and the tail part swings towards the opposite side. The fish forms a curve, then quickly the body and tail curve to other side. This makes a jerk and pushes the body forward. A series if such jerks makes the fish swim ahead. Other fins of the fish help to keep the balance of body and maintain the direction, while swimming.''

Movement of Snake
''Snakes have a long backbone. They have many thin muscles. They are connected to each other even though they are very far away from one other. Muscles also interconnect the backbone, ribs and skin. The snake's body curves into many loops. Each loop of the snake gives it a forward push by pressing against the ground. Since its long body makes many loops and each loop gives it this push, the snake moves forward very fast and not in a straight-line.''

Movement in Birds
The forelimbs are modified to form wings for flying.Their flight feathers provide a large flat surface which is light but strong.Their bones are hollow and light.The bones of hindlimbs are typical for walking and perching.The shoulder bones are strong.The breastbones are modified to hold muscles of flight which are used to move the wings up and down.