any one of the contractile fibrous bands or bundles, having the function of producing movement in the animal body, which conjointly make up the muscular system
tissues which contract when lengthened, extended, contracted, or flexed. Flexor muscles perform ( the triceps) while extensors
Earthworms travel by coordinating two kinds of muscles: circular and longitudinal muscles. Both are located under the epidermis. When the circular muscles contract, the segments become thinner (decrease in segment diameter), the earthworm lengthens and moves forward. When the longitudinal muscles contract, the segments become thicker (increase in segment diameter), and the earthworm shortens.