Pectoral Girdle

• Pectoral Girdle


  the pectoral girdle consists of the clacvcle anteriorly + the scapula posteriorly

  the paired pectoral girdles + their associated muscles form the shoulders

  anteriorly, the medial end of each clavicle joins the sternum

  the distal ends of the clavicles meet the scapulae laterally

  
• Function of the Pectoral Girdle

  the pectoral girdles attach the upper limbs to the axial skeleton + provide attachment for many of the muscles that move the upper limbs

  these girdles r v light + allow the upper limbs a degree of mobility not seen elsewhere in the body
• Pecotral Girdle Mobility Factors

  cos only the clavicle attaches to the axial skeleton, the scapula can move quite freely across the thorax, allowing the arm to move w it

  the socket of the shoulder joint (scapula's glenoid cavity) is shallow + poorly reinforced, so it does not restrict the movement of the humerus

  = good for flexibility, bad for stability
• Clavicles


  clavicles, collarbones, r slender, S-shaped bonesclavicles, collarbones, r slender, S-shaped bones

  extend horiz across the superior thorax

  
• Function of Clavicles


  beside achoring many muscles, the clavicles act as braces - they hold the scapulae + arms out laterally, away from the narrower superior part of the thorax

  also transmit compression forces from the upper limbs to the axial skeleton - pushing
• Scapular Borders


  each scapula has 3 borders:

  superior border

  medial border

  lateral/axillary border
• Scapular Superior Border


  the superior border is the shortest + sharpest border
• Scapular Medial Border


  the medial border is paralel to the vertebral column
• Scapular Lateral Border


  the thick lateral/axillary border is next to the armpit + ends superiorly in a small, shallow fossa, the glenoid cavity

  this cavity articulates w the humerus of the arm forming the shoulder joint

  
• Scapular Angles


  the scapula has 3 angles:

  superior angle

  lateral angle

  inferior angle
• Superior & Lateral Scapular Angle

  the superior scapular border meets the medial border at the superior angle + the lateral border at the lateral angle

  
• Inferior Scapular Angle


  the medial + lateral borders join at the inferior angle

  the inferior angle moves extensively as the arm is raised + lowered + is an important landmark for studying scapular movements
• Scapular Spine


  the scapular posterior surface bears a prominent spine

  the spine ends laterally in an enlarged, roughened triangular projection = acromion

  
• Acromion


  the acromion articulates w the acromial end of the clavicle, forming the acromioclavicular joint

  
• Coracoid Process of the Scapulae

  projecting anteriorly from the superior scapular border is the coracoid process

  the coracoid process helps anchor the biceps muscle of the arm

  it is bounded by the suprascapular notch (nerve passage) medially + by the glenoid cavity laterally