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Portrait of Teres major

Anatomy · Muscles

Teres major

'Lat's little helper'

Upper limb · shoulder, posterior wall of axilla

Teres major is a thick, rounded muscle running from the lower angle of the scapula to the front of the humerus, forming part of the back wall of the armpit. It adducts, extends and medially rotates the arm, working with latissimus dorsi, and is supplied by the lower subscapular nerve. It is not a rotator cuff muscle.

How to spot them

  • ▸Thick cord-like muscle from the lower shoulder blade to the front of the humerus
  • ▸Forms the lower border of the quadrangular space and part of the posterior axillary fold
  • ▸Runs beside latissimus dorsi and inserts next to its tendon
  • ▸Not part of the rotator cuff, despite lying near it

What to know

A muscle nicknamed 'lat's little helper' because it acts with latissimus dorsi

Teres major.

It arises from the lower angle of the scapula and inserts on the medial lip of the intertubercular groove

Teres major.

The muscle forming the lower boundary of the quadrangular space through which the axillary nerve passes

Teres major.

It is supplied by the lower subscapular nerve, unlike the rotator cuff muscles beside it

Teres major.

A round muscle helping to form the back wall of the armpit, along with latissimus dorsi

Teres major.

It adducts, extends and medially rotates the arm, as in pulling an oar or rope towards the body

Teres major.

Key ideas

  • It works with latissimus dorsi for extension and medial rotation, which is why it is called lat's little helper.
  • Teres minor lies above it and teres major below, with the long head of triceps passing between the two.

Quick-fire facts

  • •Origin: dorsal surface of the inferior angle of the scapula.
  • •Insertion: medial lip (crest) of the intertubercular sulcus of the humerus.
  • •Nerve supply: lower subscapular nerve (C5–C6).
  • •Actions: adducts, extends and medially rotates the arm.
  • •It forms the inferior border of the quadrangular space, which transmits the axillary nerve and posterior circumflex humeral artery.
  • •It is not part of the rotator cuff, whose muscles are supraspinatus, infraspinatus, teres minor and subscapularis.
  • •Teres means 'round' in Latin.

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