Chest Service, Erasme University Hospital, and Laboratory of Cardiorespiratory Physiology, Brussels School of Medicine, Brussels, Belgium. a
Compr Physiol. 2011 Jul;1(3):1273-300. doi: 10.1002/cphy.c100009.
This article examines the mechanics of the muscles that drive expansion or contraction of the chest wall during breathing. The diaphragm is the main inspiratory muscle. When its muscle fibers are activated in isolation, they shorten, the dome of the diaphragm descends, pleural pressure (P(pl)) falls, and abdominal pressure (P(ab)) rises. As a result, the ventral abdominal wall expands, but a large fraction of the rib cage contracts. Expansion of the rib cage during inspiration is produced by the external intercostals in the dorsal portion of the rostral interspaces, the intercartilaginous portion of the internal intercostals (the so-called parasternal intercostals), and, in humans, the scalenes. By elevating the ribs and causing an additional fall in P(pl), these muscles not only help the diaphragm expand the chest wall and the lung, but they also increase the load on the diaphragm and reduce the shortening of the diaphragmatic muscle fibers. The capacity of the diaphragm to generate pressure is therefore enhanced. In contrast, during expiratory efforts, activation of the abdominal muscles produces a rise in P(ab) that leads to a cranial displacement of the diaphragm into the pleural cavity and a rise in P(pl). Concomitant activation of the internal interosseous intercostals in the caudal interspaces and the triangularis sterni during such efforts contracts the rib cage and helps the abdominal muscles deflate the lung.
本文探讨了在呼吸过程中驱动胸壁扩张或收缩的肌肉力学。膈肌是主要的吸气肌。当它的肌纤维单独被激活时，它们会缩短，膈肌穹顶下降，胸膜压（P(pl)）下降，腹压（P(ab)）上升。结果，腹壁向外扩张，但大部分肋骨向内收缩。吸气时肋骨的扩张是由颅侧肋间隙背侧的肋间外肌、肋软骨内部分的肋间内肌（所谓的胸骨旁肋间肌）以及在人类中由斜角肌产生的。这些肌肉通过抬高肋骨并导致胸膜压进一步下降，不仅有助于膈肌扩张胸壁和肺部，还增加了膈肌的负荷并减少了膈肌肌纤维的缩短。因此，膈肌产生压力的能力得到增强。相比之下，在呼气努力时，腹肌的激活导致 P(ab)升高，导致膈进入胸腔并导致 P(pl)升高。在这种努力中，同时激活下位肋间隙的内肋间肌和胸骨三角肌，使肋骨向内收缩并帮助腹肌使肺部排气。
