Radiology of the Diaphragm as Two Muscles

Me, Stewart; Re, Hanson; A, De Troyer; Pt, Macklem

doi:10.1097/00004424-198303000-00011

Cited by 3 publications

(1 citation statement)

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“…A regional difference in muscle fibre size indicates an adaptive response to different function. The costal parts of the diaphragm have inspiratory functions not only to lower the central aponeurosis but also to expand the lower rib cage [65,66]. This finding may imply that the costal part carries relatively larger loads during contractions.…”

Section: Histochemical Profile Of Human Respiratory Musclesmentioning

confidence: 99%

Human respiratory muscles: fibre morphology and capillary supply

Mizuno

1991

Eur Respir J

101

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In man the diaphragm (DIA) and abdominal muscles comprise approximately 50% slow-twitch (ST) fibres, whereas a higher proportion (60%) is found in intercostal muscles and the scalenes. All respiratory muscles show an equal distribution of fast-twitch (FTa and b) fibres with the exception of the expiratory intercostal muscles which have few FTb fibres. The inspiratory muscles have a uniformly small fibre size, in contrast to the expiratory intercostal muscle fibres which are large. The fibre size of the inspiratory muscles is maintained with ageing, whereas that of the expiratory intercostal muscles appears to be reduced after the age of 50 yrs. Capillary supply is most abundant in the expiratory muscles followed by DIA and the inspiratory intercostal muscles. In patients with chronic obstructive pulmonary disease (COPD) it is unknown whether a reduction in fibre size of the thoracic respiratory muscles is caused by extreme use due to increased ventilatory work, or by disuse due to an increased involvement of the extrathoracic respiratory muscles. Histochemical characteristics suggest that, in normal humans, the load on the inspiratory muscles is relatively small during contractions, whereas the expiratory intercostal muscles are exposed to severe continuous activity with a heavy load.

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Section: Histochemical Profile Of Human Respiratory Musclesmentioning

confidence: 99%