Teres major
Musculus teres major
Also known as: lat's little helper
A thick, rounded muscle from the inferior angle of the scapula to the medial lip of the intertubercular sulcus. It adducts, medially rotates and extends the arm. It is not part of the rotator cuff.
Overview
Teres major arises from the dorsal surface of the inferior angle of the scapula. It runs up and laterally, passing in front of the long head of triceps, to the medial lip of the intertubercular sulcus. There it inserts just medial to latissimus dorsi, whose tendon wraps around it. Together these two muscles form the posterior axillary fold, and teres major is often called "lat's little helper" because their actions are identical: adduction, medial rotation and extension of the humerus.
Its lower border marks the end of the axillary artery, which becomes the brachial artery there. It also forms the lower boundary of the quadrangular and triangular spaces and the upper boundary of the triangular interval. Teres major is not a rotator cuff muscle, because its tendon does not blend with the joint capsule.
Anatomy
- Origin
Posterior surface of the inferior angle of the scapula.
- Insertion
Medial lip of the intertubercular sulcus of the humerus.
- Action
Adduction, medial rotation and extension of the humerus.
- Innervation
Lower subscapular nerve (posterior cord).
- Nerve roots
C5–C6 (C7)
- Arterial supply
Thoracodorsal artery and circumflex scapular artery.
- Relations
Its lower border marks the transition from axillary to brachial artery. It forms part of the posterior axillary fold and bounds the quadrangular space, triangular space and triangular interval.
Function
- Adducts and medially rotates the arm
- Extends the arm from the flexed position
Compiled from standard anatomy and physiology references — see the Muscular System sources. For education only; not medical advice.