Which group of muscles includes those that attach to the shoulder blade and the upper arm bone?

• A. Scapulocostal muscles
• B. Scapulohumeral muscles
• C. Pectoral muscles
• D. Brachiocephalic muscles

Answer: (B)

The key idea is muscles that cross the shoulder joint by linking the shoulder blade (scapula) to the upper arm bone (humerus). These are the scapulohumeral muscles, which originate on the scapula and insert on the humerus, enabling many movements of the shoulder. Classic examples are the rotator cuff muscles—supraspinatus, infraspinatus, teres minor, and subscapularis—which all arise from the scapula and attach to the humeral head, providing stability and rotation of the shoulder. Teres major also fits this pattern, as it originates on the scapula and inserts on the humerus.

Scapulocostal muscles connect the scapula to the ribs, not to the humerus, so they don’t meet the criterion of attaching to both bones involved. Pectoral muscles primarily originate on the thorax (and clavicle) and attach to the humerus or scapula in ways that don’t form the scapulohumeral group as a whole. Brachiocephalic muscles isn’t a standard grouping for muscles crossing the shoulder and isn’t used to describe this set. So the group that truly attaches the shoulder blade to the upper arm bone is the scapulohumeral muscles.