Pectoralis MajorThe pectoralis major is the large triangular musclethat forms the prominent chest muscle (fig. 1-28). Itrotates the arm inward, pulls a raised arm down towardthe chest, and draws the arm across the chest. Itoriginates in the clavicle, sternum, and cartilages of thetrue ribs, and the external oblique muscle. Its insertionis in the greater tubercle of the humerus.DeltoidThe deltoid muscle raises the arm and has its originin the clavicle and the spine of the scapula (figs. 1-28and 1-29). Its insertion is on the lateral side of thehumerus. It fits like a cap over the shoulder and is afrequent site of intramuscular injections.Biceps BrachiiThe biceps brachii is the prominent muscle on theanterior surface of the upper arm (fig. 1-28). Its originis in the outer edge of the glenoid cavity, and itsinsertion is in the tuberosity of the radius. This musclerotates the forearm outward (supination) and, with theaid of the brachial muscle, flexes the forearm at theelbow.1-20HM3F0128MASSETERSTERNOCLEIDO-MASTOIDDELTOIDPECTORALISMAJORBICEPSBRACHIIADDUCTORLONGUSGRACILISGASTROCNEMIUSSOLEUSTIBIALISANTERIORVASTUSMEDIALISVASTUSLATERALISRECTUSFEMORISQUADRICEPSSARTORIUSLATISSIMUSDORSITRAPEZIUSFigure 1-28.—Anterior view of superficial skeletal muscles.
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