Z lines are structures found in muscle cells, specifically in the sarcomeres of striated muscle tissue. They serve as the boundaries of each sarcomere, which is the basic unit of muscle contraction. The Z line is where the thin filaments, primarily made of actin, are anchored, helping to maintain the organization of the muscle fibers during contraction. In addition to their structural role, Z lines play a crucial part in the overall function of muscles. When a muscle contracts, the Z lines move closer together, allowing the thick filaments of myosin to pull on the thin filaments, resulting in muscle shortening and movement.