Trapezius Muscle

Description

Dominating the posterior neck and upper dorsum, the trapezius forms a broad superficial sheet extending from the external occipital protuberance and superior nuchal line inferiorly along the nuchal ligament to the spinous processes of C7 through T12. Its upper fibers run inferolaterally toward the lateral third of the clavicle, the middle fibers course transversely to the acromion and spine of the scapula, and the lower fibers ascend to the medial end of the scapular spine, creating the classic triangular contour over the right shoulder girdle. Deep and medial to its lateral border, you would expect glimpses of levator scapulae and rhomboid major and minor near the medial scapular margin, while the deltoid caps the lateral shoulder and the sternocleidomastoid approaches the mastoid region anteriorly. Clear landmarks. For teaching scapulothoracic mechanics, a posterior view of the trapezius matters because it lets you track how fiber direction predicts function: upper fibers elevate the scapula, middle fibers retract, and lower fibers assist depression and upward rotation during overhead reach. Clinically, this anatomy frames evaluation after spinal accessory nerve (CN XI) injury, most often iatrogenic in posterior triangle lymph node biopsy or neck dissection, where trapezius weakness leads to shoulder droop, impaired abduction above 90 degrees, and lateral scapular winging that is distinct from serratus anterior palsy. It also supports discussion of myofascial trigger points and cervicogenic headache referral from the upper trapezius near the occiput. Use this plate in gross anatomy or kinesiology courses to anchor muscle attachments and actions, and in surgical or ENT teaching materials to illustrate the relationship between the trapezius, posterior triangle boundaries, and CN XI vulnerability. It also suits rehab handouts on scapular dyskinesis and postural neck pain when paired with palpation landmarks along the clavicle and scapular spine. Anatomical accuracy verified by SciePro's Medical Advisory Board.