Muscles

• Latissimus dorsi

  • Origin: vertebral spines from T7 to the sacrum, posterior third of the iliac crest, lower 3 or 4 ribs, sometimes from the inferior angle of the scapula
  • Insertion: floor of the intertubercular groove
  • Action: Extends the arm and rotates the arm medially
• Trapezius

  • Origin: medial third of the superior nuchal line, external occipital protuberance, ligamentum nuchae, spinous processes of the vertebrae C7-T12
  • Insertion: lateral third of the clavicle, medial side of the acromion and the upper crest of the scapular spine, tubercle of the scapular spine
  • Action: elevates and depresses the scapula (depending on which part of the muscle contracts); rotates the scapula superiorly; retracts scapula
• Rhomboid major

  • Origin: spines of vertebrae T2-T5
  • Insertion: Medial border of the scapula inferior to the spine of the scapula
  • Action: Retracts, elevates, and rotates the scapula inferiorly
• Rhomboid minor

  • Origin: inferior end of the ligamentum nuchae, spines of vertebrae C7 and T1
  • Insertion: Medial border of the scapula at the root of the spine of the scapula
  • Action: Retracts, elevates and rotates the scapula inferiorly
• Flexor digitorum profundus

  • Origin: posterior border of the ulna, proximal two-thirds of the medial border of ulna, interosseous membrane
  • Insertion: base of the distal phalanx of digits 2-5
  • Action: flexes the metacarpophalangeal, proximal interphalangeal and distal interphalangeal jointx
• Flexor digitorum superficialis

  • Origin: humeroulnar head: common flexor tendon; radial head: middle 1/3 of radius
  • Insertion: shafts of the middle phalanges of digits 2-5
  • Action: flexes the metacarpophalangeal and proximal interphalangeal joints
• Flexor carpi radialis

  • Origin: common flexor tendon from the medial epicondyle of the humerus
  • Insertion: base of the second and third metacarpals
  • Action: flexes the wrist, abducts the hand
• Flexor carpi ulnaris

  • Origin: common flexor tendon and (ulnar head) from medial border of olecranon and upper 2/3 of the posterior border of the ulna
  • Insertion: pisiform, hook of hamate, and base of 5th metacarpal
  • Action: flexes wrist, adducts hand
• Biceps branchii

  • Origin: short head: tip of the coracoid process of the scapula; long head: supraglenoid tubercle of the scapula
  • Insertion: tuberosity of the radius
  • Action: flexes the forearm, flexes arm (long head), supinates
• Brachioradialis

  • Origin: upper two-thirds of the lateral supracondylar ridge of the humerus
  • Insertion: lateral side of the base of the styloid process of the radius
  • Action: flexes the elbow, assists in pronation and supination
• Deltoid

  • Origin: lateral one-third of the clavicle, acromion, the lower lip of the crest of the spine of the scapula
  • Insertion: deltoid tuberosity of the humerus
  • Action: abducts arm; anterior fibers flex and medially rotate the arm; posterior fibers extend and laterally rotate the arm
• Extensor carpi radialis longus

  • Origin: lower one-third of the lateral supracondylar ridge of the humerus
  • Insertion: dorsum of the second metacarpal bone (base)
  • Action: extends the wrist; abducts the hand
• Extensor carpi ulnaris

  • Origin: common extensor tendon and the middle one-half of the posterior border of the ulna
  • Insertion: medial side of the base of the 5th metacarpal
  • Action: extends the wrist; adducts the hand
• Infraspinatus:

  • Origin: infraspinatus fossa
  • Insertion: greater tubercle of the humerus (middle facet)
  • Action: laterally rotates the arm
• Pectoralis major:

  • Origin: medial 1/2 of the clavicle, manubrium and body of sternum, costal cartilages of ribs 2-6, sometimes from the rectus sheath of the upper abdominal wall
  • Insertion: crest of the greater tubercle of the humerus
  • Action: flexes and adducts the arm, medially rotates the arm
• Pectoralis minor

  • Origin: ribs 3-5
  • Insertion: coracoid process of the scapula
  • Action: draws the scapula forward, medialward, and downward
• Subscapularis

  • Origin: medial two-thirds of the costal surface of the scapula (subscapular fossa)
  • Insertion: lesser tubercle of the humerus
  • Action: medially rotates the arm; assists extension of the arm
• Supraspinatus

  • Origin: supraspinatus fossa
  • Insertion: greater tubercle of the humerus (highest facet)
  • Action: abducts the arms (initiates abduction)
• Teres major:

  • Origin: dorsal surface of the inferior angle of the scapula
  • Insertion: crest of the lesser tubercle of the humerus
  • Action: adducts the arm, medially rotates the arm, assists in arm extension
• Teres minor

  • Origin: upper 2/3 of the lateral border of the scapula
  • Insertion: greater tubercle of the humerus (lowest facet)
  • Action: laterally rotates the arm