The Teres Major is the stout muscle just below the infraspinatus muscle.
Origin, axillary border of the scapula, Insertion, medial surface of the humerus,
Action, rotates the humerus inward and lowers it.
The Teres Minor is situated just under the infraspinatus muscle. It is
triangular-shaped. Origin, axillary border of the scapula, Insertion, greater
tuberosity of the humerus, Action, assists the
infraspinatus to rotate the humerus.