Which muscles aid breathing by elevating the ribs and expanding the chest wall?

• A. External oblique
• B. Intercostal muscles
• C. Diaphragm
• D. Latissimus dorsi

Answer: (B)

Breathing in during inspiration expands the thoracic cavity by lifting the rib cage. The muscles that do this are the intercostal muscles that lie between the ribs, especially the external intercostals. When they contract, they pull the ribs upward and outward, widening the chest wall and increasing thoracic volume, which draws air into the lungs. The diaphragm also helps by increasing vertical space, but the action of elevating the ribs to expand the chest wall is primarily the job of the intercostal muscles. Other muscles listed aren’t the main movers here: the diaphragm handles vertical expansion, and the other muscles are more involved with trunk movement and forceful breathing rather than elevating the ribs during normal inspiration.