Muscle filaments are the basic structural components of muscle fibers, responsible for muscle contraction. They are primarily made up of two types of proteins: actin and myosin. These proteins interact in a process called the sliding filament theory, where they slide past each other to shorten the muscle, enabling movement. There are two main types of muscle filaments: thin filaments, which are primarily composed of actin, and thick filaments, which are mainly made of myosin. Together, these filaments form a repeating unit called a sarcomere, which is the fundamental unit of muscle contraction in both skeletal and cardiac muscles.