What are myofibrils primarily composed of?

Myofibrils are primarily composed of myofilaments, which are the contractile fibers found within muscle cells. These myofilaments consist of two main types: thick filaments, primarily made of the protein myosin, and thin filaments, primarily composed of the protein actin. The arrangement of these myofilaments within myofibrils is essential for muscle contraction, as they slide past one another during the contraction process, resulting in muscle shortening and generating force.

This structural organization is critical for the functioning of skeletal muscle tissue, where myofibrils contribute to the overall muscle fiber's ability to contract and produce movement. Understanding this composition highlights the fundamental role myofibrils play in the mechanics of muscle function.