It is also known as the Locomotor system. The musculoskeletal system serves the function of structural support and locomotion. It consists of different units each serving a unique function.
The name musculoskeletal system implies muscles and skeleton. These and many other structures together constitute the musculoskeletal system.
Bone, joints, ligaments, muscles, and nerves are the structures that constitute the locomotor system.
Bones function to support the framework and provide adequate protection to underlying organs. Bones articulate with each other to provide effective motion.
The ends of bone that articulate with each other are specialized structures called joints. Joints provide a range of motion to the bones. Type of joint would determine the range that a bone would be moved.
For example, upper limbs have a higher range of motion than lower limb joints.
The range of motion is the span that a bone makes in movements. This is calculated in different planes.
Ligaments are structures that span joints and connect one bone to another. For example at the knee joint, which is formed between tibia and femur, many ligaments cross from either bone to insert into other.
The basic function of ligaments is to provide stability to joint. They prevent joints from wobbling and giving away under pressure. Injury to ligaments frequently results in instability of joints.
Muscles are responsible for movements at joints. A force is needed to move a bone from one end to another. Muscles by virtue of their contractile property produce these forces that result in motion.
Typically muscles are present in opposing groups, each one producing an opposite movement. For example flexor group of muscles would flex (fold) elbow whereas the extensor group extends (straighten) it.
Muscles forces are very well coordinated. When one group contracts, other relaxes so that energy is utilized most efficiently.
Peripheral nerves carry the sensation and signals to move. They also form part of the peripheral nervous system.
All these together produce a well-coordinated musculoskeletal system.