 Dear students, in this topic we shall discuss the lever system of the body. The levers or lever systems help in movement of body parts. The bones, ligaments and muscles in an animal's body form lever systems. The muscles in the systems apply tension to their points of insertion on bones and bones in turn cause movement. Dear students, you know that in physics a lever system has three components. First, an axis or fulcrum, force or effort and a load or resistance. In the lever system of animal body, a joint forms the axis while the muscles attached to the joint provide force and a weight or load is moved. Dear students, the study of muscles and the lever systems and their mechanisms of working are studied in a branch of biology that is known as kinesiology. Dear students, now we shall discuss the types of lever systems of the body. The levers in body and in physical terms are of three types, first class levers, second class levers and third class levers. This classification depends on three factors, first the point of muscle insertion on bone, secondly its distance that is the point of insertion of the muscles distance from axis or fulcrum and length of the lever arm. The first class levers, axis or fulcrum is located between the weight and force. The axis is between the force and the resistance. The common example of this type of lever is a pair of scissors which we call kanchi. The axis is between the force and the weight or resistance or work is performed. In human body, first class levers are very few. An example that we get in humans is the joint between head and first vertebra. In this joint we see that weight or resistance is the head while axis is the joint and force is provided by the posterior muscles attached to the skull. These students, in second class levers, weight or resistance is located between axis and force. In this way, the second class levers are in the resistance and the axis and force are on the side. In common life, this type of lever is a wheelbarrow. In humans, there are many examples of second class levers. We will take the example of lower leg. Lower leg works as a second class lever when we are standing on our tip toes. In this period, the lever in which axis is formed by the metatarsal phalangeal, that is tip toes joints. While resistance is the weight of the body and force is applied by the calf muscles. Dear students, in third class levers, force is applied between resistance and the axis or phalchrum. These types of levers are most common in human body. An example of third class lever may be taken as an elbow joint. In elbow joint, axis or phalchrum is formed by the elbow joint. And resistance or weight is the forearm, wrists and hand. This is also resistance. In addition, the load we take is also weight. While force is provided by the bicep muscles when the elbow is flexed. When the elbow joint is turned, force is provided.