Latissimus Dorsi

Triceps Brachii The triceps brachii is the primary extensor of the forearm (the antagonist of the biceps brachii) (fig. 1-29). It originates at two points on the humerus and one on the scapula. These three heads join to form the large muscle on the posterior surface of the upper arm. The point of insertion is the olecranon process of the ulna. Latissimus Dorsi The latissimus dorsi is a broad, flat muscle that covers approximately one-third of the back on each side (figs. 1-28 and 1-29). It rotates the arm inward and draws the arm down and back. It originates from the upper thoracic vertebrae to the sacrum and the posterior portion of the crest of the ilium. Its fibers converge to form a flat tendon that has its insertion in the humerus. Gluteus The gluteus (maximus, minimus (not shown), and medius) are the large muscles of the buttocks, which extend and laterally rotate the thigh, as well as abduct and medially rotate it (fig. 1-29). They arise from the ilium, the posterior surface of the lower sacrum, and the side of the coccyx. Their points of insertion include the greater trochanter and the gluteal tuberosity of the femur. The gluteus maximus is the site of choice for intramuscular injections. 1-21 HM3F0129 STERNOCLEIDO- MASTOID DELTOID TRICEPS BRACHII GRACILIS GASTROCNEMIUS SOLEUS VASTUS LATERALIS SARTORIUS LATISSIMUS DORSI TRAPEZIUS GLUTEUS MEDIUS GLUTEUS MAXIMUS BICEPS FEMORIS DELTOID TEMPORALIS Figure 1-29.—Posterior view of superficial skeletal muscles.