Teres Major Anatomy

Teres Major Muscle

Origin: Dorsal surface of the lower third of the lateral border of the scapula
Insertion: Medial lip of the bicipital groove of the humerus
Actions: Internal rotation and adduction of the arm at the shoulder
Innervation: Lower subscapular nerve (C5, C6)
Blood Supply: Subscapular and posterior circumflex humeral arteries from the axillary artery

Primary Actions of the Teres Major

1. Internal rotation of the arm at the shoulder

Agonists:

  • Subscapularis
  • Deltoid (anterior part)
  • Latissimus dorsi
  • Pectoralis major

Antagonists:

  • Infraspinatus
  • Teres minor
  • Deltoid (posterior part)

2. Adduction of the arm at the shoulder

  Agonists:

  • Latissimus dorsi
  • Pectoralis major
  • Triceps brachii (long head)

  Antagonist:

  • Deltoid (middle part)
  • Supraspinatus

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Secondary Actions of the Teres Major

1. Assists with extension of the arm at the shoulder

  Agonists:

  • Deltoid (posterior part)
  • Triceps brachii (long head)
  • Latissimus dorsi
  • Pectoralis major (sternal head)

  Antagonists:

  • Deltoid (anterior part)
  • Biceps brachii
  • Coracobrachialis
  • Pectoralis major (clavicular head)