Ribs/Thorax

Question 1

Elevation/Expansion (involved with inhalation) (antagonists on depression)

Answer 1

• Anterior scalene (bilaterally)
• Middle scalene (bilaterally)
• Posterior scalene (bilaterally)
• Sternocleidomastoid (assists)
• External intercostals (assists)
• Serratus posterior superior
• Pectoralis major (all fibers may assist if arm is fixed)
• Pectoralis minor (if scapula is fixed)
• Serratus anterior (if scapula is fixed)
• Subclavius (first rib)

Question 2

Depression/Collapse (involved with exhalation) (antagonists on elevation)

Answer 2

• Internal intercostals (assists)
• Serratus posterior inferior

Question 3

Muscles of Inhalation

Answer 3

• Diaphragm
• Anterior scalene (bilaterally)
• Middle scalene (bilaterally)
• Posterior scalene (bilaterally)
• Sternocleidomastoid (assists)
• External intercostals (assists)
• Serratus posterior superior
• Quadratus lumborum
• Pectoralis major (assists with arm fixed)
• Pectoralis minor (with scapula fixed)
• Serratus anterior (with scapula fixed)
• Subclavius (first rib)

Question 4

Muscles of Exhalation

Answer 4

• Internal intercostals (assists)
• Serratus posterior inferior
• External oblique (by compressing abdominal contents)
• Internal oblique (by compressing abdominal contents)
• Transverse abdominis (by compressing abdominal contents)
• Quadratus lumborum