Body Movements: science class six
Types of joints in human body
Joints are mainly of three types. Human body has different types of joints, which are responsible for different types of movements. These joints are
(a) Immovable joints
(b) Slightly movable joints
(c) Freely movable joints
Immovable or fixed joints
Immovable or fixed joints in bone of our skull are immovable or fixed joints. They do not allow any movements. This type of joint is also found between the teeth and jaw bones, between the bones that make up the hip bones.
The only lower jaw joint in the skull is movable.
Slightly movable or freely movable joints
Slightly or freely, movement joints are those that can move freely or slightly. They are as follows:
Ball and socket joints
Pivotal joints
Hinge joints
Gliding joints
Saddle Joints
Ball and socket joints
Ball and socket type of joints are found at the conjunction of our shoulder with arms and hip bones and legs. Ball and socket joint allows the movements in all directions. In the ball and socket joint, the rounded ball type head of one bone fits into the cup shaped hollow socket of another bone.
Ball and socket joint (Fig-7)
The bone, which fit into the socket, is free to move in all the direction about the joint. Ball and socket joints are present at the meeting point of our leg with the hip bones. Because of ball and socket joint we can move our leg at the joint of leg with our hip bone, in almost circular way.
Pivotal Joint
Pivotal joint joint is present at the point where our head joints with the upper end of backbone. In Pivotal joint joint, a ring of bone rotates around a pivot (pivot means axis). Pivotal joint allows us a type of twisting movement. Pivotal joint enables us to move our head ups and down, left and right and in a circular way.
Hinge Joint
Hinge joint type of joint in our body is very much similar to the hinge of door that is why it is called hinge joint.
Hinge joint human leg (Fig-8)
Our elbow and knee has hinge joint type of joint. In hinge joint a concave surface of one bone fit into the convex type surface of other bone. Hinge joint allows the movement similar to the hinge of a door i.e. in one direction only. We can move our hand at the elbow joint in only ups and down or in backward and forward direction because of hinge joint.
Gliding joints
Gliding joints are found in our wrist and ankle. Gliding joints have flattened ends of bones, which can move against each other in slightly backward – forward and side–to–side movements. Bones at gliding joint have cartilaginous flattened ends. Gliding joint allows slight movement like a spring.
Saddle Joints
Saddle joints allow sideways and to and fro movements. Saddle joints are found in our finger bones.
Gait of animals
As we know all animals have not similar movements. Here we will study the movement of some animals like snail, snake, cockroach etc.
Due the difference in the internal and external body structure, different animals have different type of movements.
Earthworm
We can see an earthworm in the garden. In the rainy season earthworm can be seen in plenty. Watch the body structure and movement of earthworm.
earthworm (Fig-9)
We can clearly see ring like segmented body of earthworm. Earthworms have bristle like projections throughout on their body, which is called setae. With the help of setae earthworms move their body.
These bristles, i.e. setae are connected with muscles throughout at the base of the body of an earthworm. Earthworms can squeeze these muscles in different way to change the shape of their body. These changes of shapes in the body of earthworms help them in movement.
For movement, in first stage, earthworms expand the front part of their body keeping rear part fixed static on the ground. In second stage an earthworm fixes front part of the body on the ground and pulls the rear part of the body by squeezing of muscles forward. By performing this contraction and relaxation of muscles repeatedly, an earthworm becomes able to move forward.
Leeches also moves their body in similar way.
Snakes
Snakes have no legs. In spite of that, snakes can run very fast. As snake is a vertebrate, its body has a several number of vertebrae. All vertebrae are interconnected with one another by ball and socket type joints and with body muscles. These strong body muscles attached to the ribs, vertebrae and belly scales, because of which body of a snake becomes very much flexible.
snake (Fig-10)
During movement snakes make several loops. Each loop pushes against the ground which gives the body of snakes a forward push. Doing this acting repeatedly, snakes are able to move forward. Because of movements of the body side–to–side, snakes have wave like motion.
The movement of snakes is called slithering.
Snails
Snail has a unique type of structure. Snails have a flat and large muscular foot. This muscular foot secretes a slimy liquid on which snail glides very slowly over the ground and moves forward.
snail (Fig-11)
Cockroach
Cockroaches can be seen in our household easily. Cockroach has a hard covering on its body, which is called exoskeleton.
cockroach(Fig-12)
Cockroach can walk and fly too. Cockroach has three pair of legs and two pairs of wings. Legs of cockroach are joined to its body with ball and socket joint.
During walking in first stage, three legs support the body of cockroach on the ground and other three legs move the body in forward direction. And in second stage, other three legs supports the body of a cockroach while legs which previously supported its body to the ground, move its body forward. By repeating this action, a cockroach walks easily.
To fly, cockroach uses its wings. Wings of cockroach are flat, hard and of light. Wings of cockroach are attached with the body with the help of strong muscles. With the help of muscles cockroach moves its wings forward and backward, which pushes air backward and give a upward and forward thrust to its body. This makes cockroach to fly.
Birds
Birds have boat shaped body. Boat shaped body makes a bird streamlined, which reduces the friction of air and makes her able to float in air easily. Body of a bird is of light weight. Bones of a bird are hollow. Bones are filled with air which makes birds light and strong.
skeleton of a bird (Fig-13)
Birds have one pair of wing and a pair of feet both. A pair of wings and a pair of legs enables a bird fly and walk on ground both.
To fly, a birds pushes its wings ups and down and backward and forward, which give a upward and forward thrust to make the bird fly.
With the help of two feet a birds pushes the ground one by one, which give her forward movement.
Fish
Fish lives in water. Fish have special type of structure which makes them able to live in water. Fish have scales on their body. Fish have fins, which help in swimming. They have tails, which help her to keep the right direction during swimming. Fish have gills, which help in respiration under the water. Fish have boat shaped body which makes their body structure aerodynamic. Boat shapes body helps the fish in smooth movement. Fish cannot live without water.
body of fish (Fig-14)
movement of fish (Fig-15)
Fish moves in water in wavelike way. The vertebral column of fish is very flexible and can move from side–to–side. The side–to–side movement of fish forms a wave like motion of the body. The fins also help fish in moving forward and keep the correct direction. The tail fins of fish by side–to–side movement give her a forward thrust.
Summary
Movement of whole body is called locomotion
Movement of only part of body is called movement.
Cause of locomotion are
(a) In search of food
(b) In search of suitable environment,
(c) In search of water,
(d) In search of partners,
(e) To protect from enemies
Our body got its shape because of skeletal system.
A child skeleton has 300 bones while a adult skeleton has 206 bones.
We can move a part of our body because of presence of joints between two bones.
Muscles, joints of bones and nervous system are collectively responsible for the movement of body.
There are mainly three types of joints fixed, slightly movable and freely movable.
Only lower jaw in the skull can move.
Slightly and freely movable joints are ball and socket joints, pivotal joints, hinge joints, saddle joints, and gliding joints.
Ball and socket joint is present in our arm and shoulder joints and leg and hip joints.
Pivotal joint is present in between head and backbone.
Hinge joint is present in our elbow and knee.
Gliding joint is present in our wrist and ankle
Animals in which vertebral column is present are called vertebrate and in which vertebral column is not present are called invertebrate.
Different animals have different types of movements.
Reference:
All figures are taken from NCERT Books class six chapter body movements