intrinstic shoulder muscles

• Deltoid origin

  lateral clavicle, acromion, and spine of scapula
• Deltoid insertion

  deltoid tuberosity on humerus
• deltoid action (anterior,middle,posterior)

  anterior: flex and medially rotate humerus

  middle: abduct humerus

  posterior: extend and laterally rotate arm
• deltoid innervation

  axillary nerve
• Teres major origin

  inferior angle of scapula
• teres major insertion

  intertubercular sulcus
• teres major action

  extend and medially rotate humerus
• teres major innervation

  lower subscapular nerve