muscular system

1. The system in the body composed of muscle cells and tissues that brings about movement of an organ or body part. There are three kinds of muscle: skeletal muscle , which is attached to bones and allows the voluntary movement of limbs; smooth muscle , which is found in internal organs and aids in the involuntary movements that occur in the circulatory , digestive , excretory , reproductive , and respiratory systems ; and cardiac muscle , which forms the powerful walls of the heart .)