rhomboid major muscle
The rhomboid major muscle is a muscle found in the shoulder girdle.
- origin: spinous processes of T2-T5 vertebrae
- insertion: medial border of scapula from spine to inferior angle
- innervation: dorsal scapular nerve C4, C5
- arterial supply: dorsal scapular artery
- action: adducts (retracts) and internally rotates scapula to depress glenoid cavity and fix scapula to thoracic wall
The rhomboid major arises from the four spinous processes of T2-5 and the supraspinous ligaments adjoining them. The insertion of the muscle onto the scapula extends from the inferior angle to the base of the scapular spine.
The rhomboids are innervated by the dorsal scapular nerve from the C5 root of the brachial plexus. This nerve passes through the middle scalene, running deep to levator scapulae which it also supplies. It innervates the rhomboids from their deep surface.