Muscles of tho and abdomen

• Synergist


  Two muscles that perform the same action
• Antagonist


  Two muscles that oppose each other
• Pectoralis major


  • Flexes the whole arm at the shoulder joint
  • Adducts the whole arm at the shoulder
  • Helps to medially rotate the arm at the shoulder joint
• Pectoralis major as a synergist


  • Coracobrachialis (flexes and adducts arm)
  • Subscapularis (medially rotates arm)
• Pectoralis major as an antagonist

  • Teres major and latissimus dorsi (extend arm)
  • Deltoid and supraspinatus (abduct arm)
  • Infraspinatus and teres minor (laterally rotate arm)
• External intercostals


  • Elevate the ribs for inhalation
• Internal intercostals


  • Depress the ribs for exhalation
• External and internal intercostals

  Antagonists for rib movement
• Serratus anterior


  • Protracts the scapula
• Serratus anterior as a synergist

  Pectoralis minor (protracts scapula)
• Serratus anterior as an antagonist


  Trapezius and rhomboids (retract scapula)
• Pectoralis minor


  • Protracts the scapula
• Subclavius


  • Depresses the clavicle
• External oblique


  • Flexes vertebral column
  • Compresses abdominal contents to increase intra-abdominal pressure for forced exhalation
• Internal oblique


  • Flexes vertebral column
  • Compresses abdominal contents to increase intra-abdominal pressure for forced exhalation
• Rectus abdominis


  • Flexes vertebral column
  • Compresses abdominal contents to increase intra-abdominal pressure for forced exhalation
• Transversus abdominis


  • Does not flex vertebral column
  • Compresses abdominal contents to increase intra-abdominal pressure for forced exhalation
• Linea alba


  Connective tissue aponeurosis running down the midline of the abdomen
• Pyramidalis


  • Inserts on the linea alba and helps to tense it