(ĕks‵pĭ-rā'shŭn )

[Gr. ex, out, + L. spirare, to breathe]

1. Expulsion of air from the lungs in breathing. Normally the ratio of the duration of inspiration to expiration is 1:3. Exhalation takes longer than inspiration because exhalation occurs passively.

   SEE: diaphragm for illus.; inspiration; respiration .

2. Death.

active e.Expiration accomplished as a result of muscular activity, as in forced respiration. The muscles used in forced expiration are those of the abdominal wall (external and internal oblique, rectus, and transversus abdominis), the internal intercostalis, serratus posterior inferior, platysma, and quadratus lumborum.

passive e.Expiration, performed during quiet respiration, that requires no muscular effort. It is brought about by the elasticity of the lungs, and by the ascent of the diaphragm and the weight of the descending chest wall, which compress the lungs.