Anatomy of the Teres Major

 

Anatomy of the Teres Major Muscle

Overview

The teres major is a thick, powerful muscle of the posterior axillary region. It is one of the muscles connecting the scapula to the humerus and plays an important role in movements of the shoulder joint.

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Origin and Insertion

• Origin:
  Dorsal (posterior) surface of the inferior angle of the scapula

• Insertion:
  Medial lip of the intertubercular (bicipital) groove of the humerus

Key Anatomical Notes

• The teres major is one of several muscles connecting the scapula to the humerus.

• Unlike the teres minor, the teres major does not attach to the capsule of the glenohumeral joint.

• It inserts on the anterior aspect of the proximal humerus, in close proximity to:

  • Latissimus dorsi

  • Pectoralis major

  • Subscapularis

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Innervation

• Primary innervation:
  Lower subscapular nerve (C5–C6), a branch of the posterior cord of the brachial plexus

Related Muscles and Innervation

• Subscapularis

  • Inserts higher on the humerus than the teres major

  • Innervated by the upper and lower subscapular nerves (C5–C6)

• Latissimus dorsi

  • Inserts between the teres major and pectoralis major

  • Innervated by the thoracodorsal nerve (C6–C8)

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Function

The teres major produces three principal movements at the shoulder joint:

• Adduction: Pulls the humerus toward the trunk

• Medial (internal) rotation of the humerus

• Extension (retroversion) of the humerus

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Important Anatomical Structures Related to the Teres Major

Structures in close relation to the teres major muscle include:

• Posterior circumflex humeral artery

• Brachial artery

• Deep brachial (profunda brachii) artery

• Circumflex scapular artery

• Radial nerve

• Axillary nerve

• Lower subscapular nerve

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Anatomical Spaces Related to the Teres Major Muscle

1. Quadrangular Space

Boundaries

• Superior: Teres minor

• Inferior: Teres major

• Medial: Long head of triceps brachii

• Lateral: Surgical neck of humerus

Contents

• Axillary nerve

• Posterior circumflex humeral artery

Clinical Relevance

• The axillary nerve may be injured during shoulder surgery, fractures, or dislocations.

• Surgical dissection should be performed above the teres minor to minimize the risk of axillary nerve injury.

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2. Triangular Interval

Boundaries

• Superior: Teres major

• Medial: Long head of triceps brachii

• Lateral: Shaft of the humerus

Contents

• Radial nerve

• Deep brachial (profunda brachii) artery

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3. Triangular Space

Boundaries

• Superior: Teres minor

• Inferior: Teres major

• Lateral: Long head of triceps brachii

Content

• Circumflex scapular artery

Courtesy: Prof Nabile Ebraheim, University of Toledo, Ohio, USA