Trapezius
Musculus trapezius
MuscularSuperficial musclesWhole bodyLeft and right
View left in 3D View right in 3D
- What it is
- Large flat kite-shaped muscle of the upper back and neck (the pair together forms a trapezium). It arises from the external occipital protuberance and superior nuchal line, the ligamentum nuchae and the spinous processes of C7–T12, and inserts on the lateral third of the clavicle, the acromion and the spine of the scapula.
- Function
- Upper fibres elevate the shoulder (shrug) and extend the neck, middle fibres retract the scapula, lower fibres depress it; upper and lower parts together rotate the glenoid upwards for overhead reaching.
- Size
- About 45 cm tall along the spine, up to ~1 cm thick in the neck.
- Clinical note
- Supplied by the accessory nerve (CN XI), which can be injured in surgery of the posterior triangle of the neck, leaving a drooping shoulder; note the tendinous "diamond" at the neck–back junction.