Joints and their Types

Body and its Movements

There are so many movements that happen in our bodies. Sit absolutely still and observe the movements taking place in your body. You must be blinking your eyes from time to time. There will be movements in your body as you breathe. 

Different parts of your body move while you remain at the same place. A few examples of when this happens are – your hand moves when you are writing in your notebook, your head moves when you turn and look at your friend. 

You also move from one place to another - you get up and go to your teacher, or to the play ground, or go home after school. You walk, run, skip, jump and move from place to place. 

There are different ways how animals move from place to place. For example, a cow uses its legs to walk, a snake uses its whole body to slither or crawl, a bird uses its wings to fly, and a fish uses its fins to swim. Walking, crawling, flying and swimming - these are only a few of the ways in which animals move from one place to another. 

Joints

Our body is capable of many movements. You can rotate your arm at the shoulder in a circular movement and stretch your arm sideways. You can bend your arm at the elbow and the leg at the knee. You can stretch your arm sideways and bend your arm to touch your shoulder with your fingers. Through all these movements you will notice that parts of your body can do various functions like – the ability to rotate completely or partially, can bend, lift objects or does not move at all.

You might have noticed that you are able to bend or rotate our body in places where two parts of the body seem to be joined together — like elbow, shoulder or neck. These places are called joints. If our body has no joints, it would not be possible for us to move in any way at all. 

Have you thought about what exactly is joined together at these joints? If you press your fingers against the top of your head, shoulder, hands and legs including the fingers and toes, you get a feel of something hard pressing against your fingers. The hard structures are the bones. 

Bones cannot be bent. So, how do we bend our elbow? It is not one long bone from the upper arm to our wrist. It is different bones joined together at the elbow. Similarly, there are many bones present in each part of the body. We can bend or move our body only at those points where bones meet. 

Types of Joints

There are different types of joints in our body to help us carry out different movements and activities. 

Ball and Socket Joints

The Ball and socket joint consist of a rounded bone with a ball-shaped surface at one end which fits into the cup-like depression of another bone. This rounded bone with a ball-shaped surface is your arm and has the ball at its end. The cup-like depression is the part of the shoulder to which your arm is joined. The rounded end of one bone fits into the cavity (hollow space) of the other bone. Such a joint allows movements in all directions. Another example of this joint is the hip. 

Pivotal Joint

The joint where our neck joins the head is a pivotal joint. It allows us to bend our head forward and backward and turn the head to our right or left. In a pivotal joint a cylindrical bone rotates in a ring. Movement at such a joint is limited to rotation around a central axis. 

Hinge Joints

In the hinge joint, the convex surface of one bone fits into the concave surface of another, as in the elbow and the joints of the fingers. The hinge joint allows only a back and forth movement. This joint resembles the hinge of a door in that it permits movement in one plane only. Open and close a door a few times. If you observe the hinges of the door carefully you will see that they allow the door to move only back and forth and in no other direction. 

Fixed Joints

There are some bones in our head that are joined together at some joints. The bones cannot move at these joints. Such joints are called fixed joints. When you open your mouth wide, you can move your lower jaw away from your head, but if you try to move your upper jaw, you will be able to move it. There is a joint between the upper jaw and the rest of the head which is a fixed joint.   

Summary

  • The bone joints are of various kinds depending on the nature of joints and direction of movement they allow.Joints aid in body movements.
  • Joints help connect the bones together.
  • The types of joints are - Ball and Socket Joints, Pivotal Joint, Hinge Joint and Fixed Joints. 

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