The palmaris longus muscle is one of five muscles that act at the wrist joint. The palmaris longus muscle is a long muscle that runs to the palm and activates flexibility at the wrist. Muscles assist in movement, blood flow, speech, heat production, body shaping, and protection of some internal organs. How muscles attach depends on function and location, and may attach directly to skin or bone. Tendons attach bone to muscle. Ligaments attach bone to bone. An aponeurosis is a strong, flat connective tissue that attaches to muscle. Fascia is tissue that connects muscle to muscle or muscle to skin. The two ends of a skeletal muscle’s attachment are ‘insertion’ and ‘origin.’ The insertion end is the part that attaches to the moveable bone that will move when contracted. The palmaris longus muscle starts up near the elbow and runs across the middle of the forearm, where it inserts on the palmar aponeurosis. The palmaris longus muscle is absent in approximately 14 percent of the population, but has no affect on tightening and clenching ability. When present, the palmaris longus muscle is visible at the palm side of the wrist when flexed.