Mechanism by which air is drawn into the lungs. A combination of movements of the ribs upwards and outwards, and of the diaphragm downwards reduces the intrapulmonary and intrapleural pressure, which in turn causes air to rush into the lungs. During resting inspiration, the ribs are fixed by the scalenus muscles, and contraction of the external intercostals elevates the ribcage, while the diaphragm contracts and flattens downward. Additional muscles become active during exercise when inspiration is a much more dynamic process: the scalenes elevate the first and second ribs, the sternocleidomastoids elevate the sternum, and the extensors of the back and trapezius muscle may also take part in the process.
Subjects: Sports and Exercise Medicine.