Myofibrils

Myofibrils are long, thread-like structures within muscle cells that are responsible for the muscle's ability to contract and generate force. They are made up of repeating units called sarcomeres, which contain the proteins actin and myosin. When a muscle contracts, these proteins slide past each other within the sarcomeres, shortening the myofibrils. This process allows your muscles to produce movement and strength. Myofibrils are essential for muscle function and make up most of the muscle cell's interior, providing the structure necessary for muscle contraction at a microscopic level.