II. Naming Skeletal Muscles

A. Names of the 700+ muscles are based on a few characteristics 1. Direction of muscle fibers in relation to the midline of the body a. Rectus- run parallel to the midline b. Transverse run perpendicular to midline c. Oblique run diagonally to the midline

2. Location- named for the structure that it is near 3. Size- relative size of the muscle a. Maximus/minimus- largest and smallest b. Longus/brevis- longest and shortest 4. Number of origins- number of tendons for the origin a. Biceps, triceps, quadriceps

5. Relative shape of the muscle a. Deltoid- triangular b. Trapezius- trapezoid c. Serratus- saw toothed d. Rhomboidus- rhomboid or diamond shape 6. Sites where the muscle originates and inserts

7. Action- principle action of the muscle a. Flexor- decreases an angle at the joint b. Extensor- increases angle at the joint c. Abductor- moves bone away from the midline d. Adductor- moves bone toward midline

e. Levator- upward movement f. Depressor- downward movement g. Pronator- turn palm down ro posterior h. Supinator- turn palm up or anteriorly i. Sphincter- closes an opening j. Tensor- makes a body part more rigid k. Rotator- moves a bone around an axis