trapezius muscle
key facts
Origin
Descending part (superior fibers): medial third of the superior nuchal line, external occipital protuberance, nuchal ligament
Transverse part (middle fibers): spinous processes and supraspinous ligaments of vertebrae T1-T4 (or C7-T3)
Ascending part (inferior fibers): spinous processes and supraspinous ligaments of vertebrae T4-T12
Insertion
Descending part (superior fibers): lateral third of clavicle
Transverse part (middle fibers): medial acromial margin, superior crest of spine of scapula
Ascending part (inferior fibers): lateral apex of the medial end of scapular spine
Innervation
Motor: accessory nerve (CN XI)
Motor/Sensory: anterior rami of spinal nerves C3-C4 (via cervical plexus)
Descending part (superior fibers)
- Scapulothoracic joint: draws scapula superomedially
- Atlantooccipital joint: extension of head and neck, lateral flexion of head and neck (ipsilateral)
- Atlantoaxial joint: rotation of head (contralateral)
Transverse part (middle fibers)
- Scapulothoracic joint: draws scapula medially
Ascending part (inferior fibers)
- Scapulothoracic joint: Draws scapula inferomedially
Blood supply
Occipital artery (descending part), superficial or transverse cervical artery (transverse part), dorsal scapular artery (ascending part)