Identify the muscles that act on the thorax and abdominal wall in the figure below:
External intercostal muscle
Internal intercostal muscle
Diaphragm
Rectus abdominis muscle
External intercostal muscle: elevates the ribs and is innervated by the intercostal nerves.
Internal intercostal muscle: depresses the ribs and is innervated by the intercostal nerves.
Diaphragm: expands the thorax, producing inspiration, and is innervated by the phrenic nerve.
Rectus abdominis muscle: flexes the trunk and is innervated by the lower intercostal nerves.