You have seen people performing different activities like walking, running, swimming, etc. Do you enjoy doing physical exercise? You move your hands and legs while playing cricket. You rotate your arm while bowling. Bend your arm at the elbow and the leg at the knee. Stretch your arm sideways. Bend your arm to touch your shoulder with your fingers. Now, you know that we are able to move a few parts of our body easily in various directions and some only in one direction. The human body can move different parts of its body because of the presence of Joints.
Do you notice that we are able to bend or rotate our body in places where two parts of our body seem to be joined together like the elbow, shoulder, or neck? These places are called joints.
Joints connect two different parts of the body and help in body movements. Now, you must be thinking that what exactly are joined together at these joints? Let’s find the answer. Press your fingers against your head, face, neck, shoulder, and other parts of the body. Do you get a feel of something hard pressing against your fingers?
The hard structures are bone. Bones cannot be bent, but we can bend or move our body only at those points where bones meet. You might be thinking that do animals have joints too? Actually different animals have a different framework. Different types of animals move differently. For example, elephants use their legs to walk while snakes use their body to slither.
Birds and insects on the other hand use their wings to fly, while fish use their fins to swim through water. Plants do not move from one place to another, as they are attached to soil but they do have movements. They do not have joints but the branches of plants move towards the source of light and their roots move downwards away from light.
You have studied how joints are important in our body. In the absence of joints in our body, it would not be possible for us to move in any way at all. There are different types of joints in our body to help us carry out different movements and activities.
Types of Joints:
- Ball and Socket Joints
- Pivotal Joints
- Hinge Joints
- Fixed Joints
Ball and Socket Joints
Many different types of joints exist in the human body, but the kind which allows the greatest range of motion is the ball and socket joint. One end of a bone is rounded and ball-like and fits into a cup-like depression of the other bone. The function of this kind of joint is to connect two bones but to do it in such a way that the bone with a rounded end is able to move in all directions. Let’s do an activity to understand it.
Roll a strip of paper into a cylinder. Take an old rubber or plastic ball and make a small hole in it. Now, push one end of the paper cylinder into it. Put the ball in a small bowl having a hemispherical shape. You will find that the ball attached to the paper cylinder is able to rotate freely inside the bowl.
Now, imagine the paper cylinder as your arm and the ball as its end.
The bowl is like the part of the shoulder to which your arm is joined. The rounded end of one bone fits into a cup-like cavity, called the Socket, of the other bone. Such a joint allows movements in all directions. You might have seen how a swimmer moves his arms and legs in the water. The arm movement is possible because of the ball and socket joint. The ball and socket joint is also present between the hip and the leg.
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.
You often must have opened and closed doors a few times. Have you observed the hinges of the door carefully? They allow the door to move back and forth. Similarly, the elbow has a hinge joint that allows only a back and forth movement
There are some bones in our head thatare joined together at some joints. Thebones 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, isn’t it? Try to move your upper jaw, now. Are you able to move it? No, as there is a joint between the upper jaw and the rest of the head which is a fixed joint.