|Derivation||Rounded (teres) and larger.|
|Origin||Lower angle of the scapula.|
|Insertion||Anterior surface of the humerus, below the head.|
|Action||Adducts the upper arm and rotates it medially (inward).|
Teres major is a rounded form with a horizontal and slightly diagonal axis. It points conveniently at the lower angle of the scapula, an important skeletal landmark.
Unlike infraspinatus above, teres major goes to the front of the humerus instead of the back. Therefore, where the line of teres major meets that of triceps, the latter usually demands precedence.
Teres major joins with latissimus dorsi to form the posterior wall of the armpit. The sharp turn in the wall from a more-vertical to a more-lateral direction indicates teres major.