👉 Muscular cells are the specialized tissue in the human body that is responsible for producing and secreting muscle fibers. These muscle fibers are responsible for movement, strength, and endurance. The muscles are composed of millions of tiny muscle fibers arranged in a network called myofibril, which can be further divided into myofilaments. Each myofilament contains one or more actin or myosin molecules that form the sarcomere, which is the central component of the muscle fiber.