Superficial Muscles Anterior & Posterior Thorax -Scapula+Arm

• Superficial Thorax Muscles


  most superficial thorax muscles = extrinsic shoulder muscles, which run from the ribs + vertebral column to the shoulder girdle

  they can fix the scapula in place/move it to increase the range of arm movements

  
• Anterior Muscles of the Thorax


  the anterior muscles of the thorax:

  pectoralis major

  pectoralis minor

  serratus anterior

  subclavius

  except for the pectoralis major, which inserts into the humerus, all muscles of the anterior group insert into the pectoral girdle

  
• Posterior Muscles of the Thorax


  latissimus dorsi

  trapezius muscles (superficially)

  levator scapulae (underlying)

  rhomboids

  the latissimus dorsi insert into the humerus - more concerned w moving arm than the scapula

  
• Movements of the Pectoral Girdle


  displacing the scapula - elevation/depression, rotation, lateral (forward) movements + medial (backward) movements

  the clavicvles rotate around their own axes to provide stability + precision to scapular movements
• Stabilisation & Depression of the Shoulder Girdle


  except for the serratus anterior, the anterior muscles stabilise + depress the shoulder girdle

  most scapular movements r promoted by the serratus anterio muscles anteriorly + by posterior thoracic muscles

  the arrangement of muscle attachments to the scapula is such that one muscle cannot bring about a simple linear movement on its own

  to effect scapular movements, several muscles must act in combo
• Elevation of the Scapula


  the prime movers of scapular elevation = levator scapulae + the superior fibres of the trapezius

  when acting together to shrig the shoulder, their opposite rotational effects counterbalance each other
• Depression of the Scapula


  the scapula is depressed largely by gravity (weight of arm), but when it is depressed against resistance, the inferior part of the trapezius, the pectoralis minor + the serratus anterior (along w the latissimus dorsi) r active
• Abduction/Protaction of the Scapula


  posteromedial movement (adduction + retraction) of the scapula is effected mainly by the middle part of the trapezius together w the rhomboids
• Upward Rotation of the Scapula


  upward rotation of the scapula so that the glenoid cavity points upward (as in lifting the arm above the head) is accomplished mainly by the serratus anterior + the superior part of the trapezius
• Downward Rotation of the Scapula


  downward rotation of the scapula so that the glenoid cavity points downward (paddling in a canoe) is accomplished by the rhomboids + levator scapulae