Table 1.

The Primary and Accessory Muscles in Inhalation and Exhalation

	Muscles of Inhalation	Muscles of Exhalation
Primary	Diaphragm Parasternal internal intercostals Upper and lateral external intercostals Levatores costarum Scalenes (less active during normal breathing)	Elastic recoil* Diaphragm Pleura and costal cartilage*
Accessory	Sternocleidomastoid Upper trapexius Serratus anterior Latissimus dorsi Iliocostalis thoracis Subclavius Omohyoid	Interosseous internal intercostals Abdominal muscles Transversus thoracis Subcostales Iliocostalis lumborum Quadratus lumborum Serratus posterior inferior Latissimus dorsi

Listed above is a comprehensive list of the primary and accessory muscles that are associated with proper breathing patterns. When there is a BPD the accessory muscles replace the primary movers.³

^*Primary non-muscular anatomic structures associated with breathing.