The triangular muscle of the shoulder region that forms the rounded flesh of the outer part of the upper arm, and passes up and over the shoulder joint. The wide end of the muscle is attached to the shoulderblade and the collarbone. The muscle fibres meet to form the apex of the triangle, which is attached to the humerus (upper-arm bone) halfway down its length. The central, strongest part of the muscle raises the arm sideways. The front and back parts of the muscle twist the arm.
Deltoid |
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