Trapezius

Back Muscles

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The Trapezius is a large superficial muscle that extends longitudinally from the occipital bone to the lower thoracic vertebrae and laterally to the spine of the scapula (shoulder blade). Its functions are to move, rotate, and stabilize the scapula.

Anatomy

The trapezius has three functional regions: the superior region (descending part), which supports the weight of the arm; the intermediate region (transverse part), which retracts the scapula; and the inferior region (ascending part), which medially rotates and depresses the scapula.

Origin and insertion

The trapezius muscle resembles a trapezium (trapezoid in American English), or diamond-shaped quadrilateral. The word "spinotrapezius" refers to the human trapezius, although it is not commonly used in modern texts. In other mammals, it refers to a portion of the analogous muscle.

Function

The trapezius has several functions: the upper part of the muscle can be used to shrug the shoulders. When the entire muscle is active, it can pull the head backwards or to the side. If lower fibers are active, they can draw the shoulder blades together. The upper and lower fibers can work together to draw the head straight back.

Clinical significance

The trapezius muscle can be a source of headache due to the tension in the fibers of the muscle. It can be relieved with techniques that include physical therapy, massage, biofeedback, and other relaxation exercises.

See also

• List of muscles of the human body
• Scapula
• Occipital bone
• Thoracic vertebrae