Muscles have contractile proteins. The contraction and relaxation of these contractile proteins brings about the movement of body parts. Bones are supporting tissues that form the structure of the body. Blood is a fluid connective tissue that transports oxygen and nutrients and cartilage provides support and flexibility.By contractile proteins, we mean actin (thin filament) and myosin (thick filament). Each actin filament is composed of two helical “F” actin (filamentous actin) and each ‘F’ actin is made up of multiple units of ‘G’ actin.