How do muscles in the thorax cause air to enter the lungs during breathing?
use of the diaphragm, external intercostals, and pectoralis minor used in forced inhalation Intercostal muscles are several groups of muscles that run between the ribs, and help form and move the chest wall. There are three principal layers; the external intercostal muscles, which aid in quiet and forced inhalation. They originate on ribs 1-11 and have their insertion on ribs 2-12. The external intercostals are responsible for the elevation of the ribs, and expanding the transverse dimensions of the thoracic cavity. Located around the ribs the internal intercostal muscles, which aid in forced expiration (quiet expiration is a passive process). They originate on ribs 2-12 and have their insertions on ribs 1-11. The internal intercostals are responsible for the depression of the ribs decreasing the transverse dimensions of the thoracic cavity. the innermost intercostal muscle, the deep layers of the internal intercostal muscles which are separated from them by the neurovascular bundle. B
