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In-Depth Information
movement. Rotation of the head to around 180 degrees can be achieved
by the horizontal rotation of the neck, facilitated by the flexibility of the
vertebrae in the cervical region of the spine.
There are a number of muscles that form parts of the shoulder and are
connected to a series of bones and joints to accommodate movement. The
illustration shows how these muscles are connected to the ribs, the sternum,
the scapula, the clavicle, the spinal column, and the humerus. The movement
of both the shoulder girdle and the shoulder joint allows for movements of
the arm. It is this structure that allows for combined and cooperative actions
of both the shoulder and the arms; this in turn enables the range of arm
movement to be extensive.
FIG 5.4
Shoulder construction.
Arms
The upper arm bone is the humerus, which is long and strong and allows for
the transmission of power through leverage. The lower arm is supported by
a two-bone structure: the ulna and the radius. These bones allow for rotation
of the lower arm at the elbow joint. The biceps are the primary muscles that
