Trapezius

Musculus trapezius

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The trapezius is a large diamond-shaped muscle with three functional regions that together control the scapula: upper fibers elevate, middle fibers retract, and lower fibers depress and assist upward rotation. It is trained by shrugs (upper), rows and face pulls (middle), and Y-raises and overhead pressing (lower), and is essential for healthy scapular positioning and overhead strength.

Actions

Scapular elevation, Scapular retraction, Scapular depression, Scapular upward rotation, Neck extension

Origin

External occipital protuberance, medial third of the superior nuchal line, ligamentum nuchae, and spinous processes of C7-T12

Insertion

Lateral third of the clavicle, acromion, and spine of the scapula

Innervation

Motor: accessory nerve (CN XI); proprioception: ventral rami of C3-C4

Blood supply

Transverse cervical artery (superficial branch / superficial cervical artery) and dorsal scapular artery

Heads

Descending (upper) fibers, Transverse (middle) fibers, Ascending (lower) fibers

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