The muscular system moves the body. The body has more than 600 muscles, each of which consists of special fibres that can contract. When a muscle contracts, it pulls the tissue to which it is attached. This pulling results in movement.
The muscles of the human body can be divided into two main types: (1) skeletal muscles and (2) smooth muscles. A third kind of muscle, cardiac muscle, is found only in the heart. It has features of both skeletal muscle and smooth muscle.
The skeleton of an adult consists of more than 200 bones. The skeleton forms a strong framework that supports the body. It also helps protect the internal organs. For example, the brain is shielded by the skull, the spinal cord by the spinal column, and the heart and lungs by the ribs.