Trapezius

The trapezius muscle is a large flat superficial triangular muscle covering the back of the neck and shoulder.

It is sometimes described in terms of three parts or regions of the trapezius muscle. They are the:

• Superior (upper) fibres, also called the 'descending fibres'
• Middle fibres, and the
• Inferior (lower) fibres, also called the 'ascending fibres'.

Origin, Insertion and Actions of the (whole) Trapezius muscle:

It is not surprising that such an extensive muscle has so many actions. Different textbooks and websites list and describe the actions of the trapezius muscle in slightly different ways. There is no single consistent number of actions of trapezius muscle. The most detailed descriptions indicate the actions of specific parts (groups of fibres) of this muscle, together with examples of movements caused or supported by the trapezius muscle. An example of a short list of its actions is:

• Stabilises the scapula
• Elevation, rotation, and adduction of the scapula
• Some extension and rotation of the neck.

Overall, many of the actions of the trapezius muscle involve moving the scapula bone and/or the clavicle bone or head/neck.

The trapezius muscle is labelled on the diagrams of the human anterior muscles and the human posterior muscles.

The word 'trapezius' is derived from the Greek word trapezoides, which means 'table shaped'.