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Posterior Scapula Muscles
- The muscles of the posterior scapula are innervated by the brachial plexus
- Originates in the supraspinous fossa of the scapula
- Inserts on the greater tubercle of the humerus (specifically, the superior facet of the tubercle)
- Abducts the humerus.
Infraspinatus
- Originates in the infraspinous fossa of the scapula
- Inserts on the greater tubercle of the humerus (specifically, the middle facet)
- Laterally rotates the humerus.
Teres minor
- Originates on the lateral scapular border (specifically, the proximal 2/3rds of the lateral border)
- Inserts on the greater tubercle of the humerus (specifically, the lower facet)
- Laterally rotates the humerus.
Teres major
- Originates on the posterior surface of the inferior angle of the scapula
- Inserts on the intertubercular groove of the anterior humerus (specifically, on the medial lip)
- Adducts the humerus, and, because of its anterior insertion, medially rotates the arm.
Long head of triceps brachii
- Originates on the infraglenoid tubercle
- Inserts on the olecranon process of the ulna (via common triceps brachii tendon).
- Is an accessory adductor and extensor of the arm (it also works with the medial and lateral heads of triceps brachii to extend the forearm).
Clinical correlations:
- The posterior shoulder muscles are arranged so that discrete spaces are created, through which neurovascular structures pass.
The quadrangular space comprises the space between:
- Teres minor
- Humeral neck
- Teres major
- The long head of triceps brachii.
- The quadrangular space encompasses the axillary nerve and posterior circumflex artery.
The triangular space comprises the space between:
- Long head of triceps brachii
- Teres major
- Teres minor
- The triangular space encompasses the circumflex scapular artery.
Triangular interval comprises the space between:
- Long head of triceps brachii
- Humeral shaft
- Teres major
- The triangular interval encompasses the deep brachial artery and the radial nerve.