The right & left trapezius together form a trapezium (Diamond shape) that covers the upper half of the back.

ORIGIN:

Upper fibres of the trapezius- C7 spinous process, External occipital protuberance, medial third of the superior nuchal line of the occipital bone & ligamentum nuchae.

Middle fibres of the trapezius- C7 spinous process, T1,T2 & T3 spinous process, corresponding supraspinous ligaments.

Lower fibres of the trapezius- T4-T12 spinous process & corresponding supraspinous ligaments.

INSERTION:

Upper fibres of the trapezius- after originating, the fibres run downward & laterally to insert into posterior border of the lateral one-third of the clavicle.

Middle fibres of the trapezius- medial border of the acromion & superior lip of the posterior border (crest) of the spine of the scapula.

Lower fibres of the trapezius- after originating, the fibres run upward & laterally to converge near scapula & end in aponeurosis overdeltoid tubercle(apex of triangular surface) at the medial end of the spine with the bursa intervening.

INNERVATION:  Spinal accessory nerve & Proprioceptive fibres from vental rami of C3 & C4.

BLOOD SUPPLY: Superficial branch of transverse cervical artery or superficial cervical artery

ACTIONS:

Trapezius causes movement at the spine as well as at the scapula. It produces movement at scapula when the spinal origins are stable and it produces movement at the spine when scapula is stable. Its main function is to stabilize and move the scapula. For the movement at the head and neck it needs to keep the scapular attachment stable.
Trapezius produces actions either by contracting bilaterally or unilaterally. Its fibres also have different actions as they run in different directions. However during the functional movements, each of these fibres needs to work in coordination to produce a smooth action.

Palpation:

Upper Trapezius: The upper trap may be palpated from the base of the skull to the base of the neck and across the top of the shoulder girdle.

Position : Lying  in prone, gently squeeze the most superficial layer of muscle at the upper cervical spine. Ask the patient to  lift their head – you  feel the density of this layer quickly increase as the upper trap contracts – follow those same fibers down across the top of the scapula.

Gently elevate and relax their shoulder girdle as you palpate may help you trace the fibers from the base of the neck to lateral clavicle .

Note: if you feel too deep when palpating the traps at the cervical spine you will be palpating the splenii. These muscles are easy to identify, they feel like two near-vertical bars or cylinders of muscle. They course up and down the back of the neck, they  do not course over the shoulder girdle.

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