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Pectoral Muscles
The pectoral is a term relating to the chest. The
"pectoralis major" is a large, fan-shaped muscle that covers
much of the front upper chest. It begins at the breastbone (sternum) and
the cartilage of the second to the sixth ribs and is attached to the
collarbone (clavicle) to converge on the upper arm bone (humerus) just
below the shoulder. Its main use is in moving the arm across the body. The
"pectoralis minor" is a smaller, triangular muscle beneath the
pectoralis major. It stems from the third to fifth ribs and converges at
the shoulder blade (scapula), which it moves up and down. |
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Deltoid Muscles
The deltoid is the triangular muscle of the shoulder
that forms the rounded flesh of the outer part of the upper arm. It passes
up and over the shoulder joint. The wide end of the triangle is attached
to the shoulder blade (scapula) and the collarbone (clavicle). The apex of
the triangle is attached to the upper arm bone (humerus), about halfway
down its length. Its strongest point is the central section, which raises
the arm sideways. The front and back parts of the muscle twist the arm.
The ligaments which connect the muscles to the bone endings are called
"deltoid ligaments." Deltoid comes from the Greek word "deltoeides,"
meaning shaped like a (river) delta. |