shoulder

• Anterior Fibres of Deltoid:

  O: Anterior border of the lateral 1/3 of the clavicle

  R: Obliquely down and posteriorly

  I: Deltoid tuberosity on the lateral surface of the humerus via a short thick tendon

  A: Strong flexor and medial rotator of the GHJ

  NS: Axillary nerve (C5, 6)
• Middle Fibres of Deltoid

  O: Lateral margin of the acromion process via 4 tendinous slips

  R: Downwards

  I: Deltoid tuberosity via a short thick tendon

  A: Abduction (in the line of the scapula and not the anatomical position) beyond the initial 20

  NS: Axillary nerve (C5, 6)
• Posterior Fibres of Deltoid

  O: Lower lip of the spine of the scapula

  R: Obliquely down and anteriorly

  I: Deltoid tuberosity on the lateral surface of the humerus via a short thick tendon

  A: Strong extensor and lateral rotator of the GHJ

  NS: Axillary nerve (C5, 6)

  
  

  Function: Acts as antagonist to pectoralis major and latissimus dorsi during adduction of the arm to counteract medial rotation
• Clavicular Head of Pectoralis Major

  O: Smaller head arising from the medial ½ of the anterior surface of the clavicle

  R: Down and lateral

  I: Via a flat tendon to the lateral lip of the intertubercular groove (covering the long head of biceps tendon)

  Forms the anterior lamina (layer) which runs to the lower part of the groove

  A: Flexes the GHJ to 90 degrees, horizontally flexes, adducts and medially rotates

  NS: Medial (C8, T1) and lateral (C5, 6, 7) pectoral nerves
• Sternal Head of Pectoralis Major

  O: Larger head arising from manubrium and body of the sternum, the adjacent parts of the upper 6 costal cartilages & the aponeurosis of the external oblique

  R: Horizontal & superolateral

  I: Via a flat tendon to the lateral lip of the intertubercular groove (covering the long head of biceps tendon). Forms the posterior lamina (layer) which passes upwards and behind the anterior lamina to the upper part of the groove

  A: Extends the flexed arm, adducts and medially rotates

  NS: Medial (C8, T1) and lateral (C5, 6, 7) pectoral nerves
• Coracobrachialis

  O: From a rounded tendon on the apex of the coracoid process on the scapula

  R: Inferiorly and laterally

  I: Roughened area halfway down the medial side of the humeral shaft, opposite the deltoid tuberosity

  A: Adduction of the GHJ; may assist in some flexion but only in a small role

  NS: Musculocutaneous nerve (C5, 6, 7)
• Latissimus Dorsi

  O: Spinous processes of the lower 6 thoracic vertebrae and all the lumbar and sacral vertebrae (via thoracolumbar fascia). Intervening supraspinous and interspinous ligaments. Outer lip of the posterior part of the iliac crest

  R: Upwards and laterally

  I: En-route, some fibres attach to the outer surfaces of the lower 3 or 4 ribs and the inferior angle of the scapula. Floor of the intertubercular groove via thin flattened tendon, anterior to the teres major tendon

  A: Extensor of flexed arm, adductor and medial rotator of the GHJ

  NS: Thoracodorsal nerve (C(6), 7, 8)
• Teres Major: Thick muscle forming part of the posterior aspect of the axilla with Latissimus dorsi

  O: Dorsal surface of the inferior angle of scapular, below teres minor

  R: Upwards, anteriorly and laterally

  I: Fibres attach via a broad flat tendon to the medial lip of the intertubercular groove of humerous (tendon separated from lat. dorsi tendon by a bursa)

  A: Adducts and medial rotates GHJ; may also assist with extension of the flexed shoulder

  NS: Lower subscapular nerve (C5, 6)

  Function: resists upward displacement of HOH during active contraction of deltoid