L5.5.3: Chest Muscles

• CHEST MUSCLES

  [a] Pectoralis Major

  [b] Pectoralis Minor

  [c] Serratus Anterior

  [d] Intercostal Muscle / Intercostalis

  
• Pectoralis Major

  ○ Large, fan-shaped muscle covering the upper part of the chest

  ○ Originates from the sternum, shoulder girdle, and the first six ribs

  ○ Inserts to the proximal end of the humerus

  ○ Forms the anterior wall of the axilla

  ○ Movement: Adduct and flex the arm
• Pectoralis Minor

  ○ Triangular in shape

  ○ Located under the pectoralis major

  ○ Also form the anterior wall of the axilla

  ○ Originates from the margins of the 5th ribs adjacent to the costochondral junction
• Serratus Anterior

  ○ Fan-shaped muscle

  ○ Originates on the superolateral surfaces of the 1st to 8th ribs or the 1st to 9th ribs of the lateral wall of the thorax

  ○ Inserts along the superior angle, medial border, and inferior angle of the scapula
• Intercostal Muscle / Intercostalis

  ○ Deep muscles found between the ribs
• EXTERNAL INTERCOSTALS

  • Lie toward the lateral edge of the ribcage
  • Important in breathing as they help raise the ribcage when inhaling
• INTERNAL INTERCOSTALS

  • Lie deep and medial to the external intercostals
  • Depress the rib cage; help to move air out of the lungs when you exhale forcibly