HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Troyer, A. D. Articles by , T. A. W. Search for Related Content PubMed PubMed Citation Articles by Troyer, A. D. Articles by , T. A. W.

The canine parasternal and external intercostal muscles drive the ribs differently

André De Troyer and Theodore A. Wilson *

1. In the dog, the elevation of the ribs during inspiration results from the combined actions of the parasternal and external intercostal muscles. In the present studies, the hypothesis was tested that co-ordinated activity among these two sets of muscles reduces the distortion of the rib cage.

2. During spontaneous inspiration before or after section of the phrenic nerves, the ribs moved cranially and outward in the same way as they did during passive inflation. However, whereas the sternum moved cranially during passive inflation, it was displaced caudally during spontaneous inspiration.

3. When the parasternal intercostal muscles were selectively denervated, both the sternum and the ribs moved cranially, but the rib outward displacement was markedly reduced. In contrast, when the external intercostals were excised and the parasternal intercostals were left intact, the sternum continued to move caudally and the outward displacement of the ribs was augmented relative to their cranial displacement.

4. These observations establish that the external intercostal muscles drive the ribs primarily in the cranial direction, whereas the parasternal intercostals drive the ribs both cranially and outward. They also indicate, in agreement with the hypothesis, that co-ordinated activity among these two sets of muscles displaces the ribs on their relaxation curve.

5. However, this co-ordinated activity also displaces the sternum caudally. Although this distortion requires an additional energy expenditure, it enhances the outward component of rib displacement which is more effective with respect to lung expansion.

This article has been cited by other articles:

				A. D. Troyer and D. Leduc Role of pleural pressure in the coupling between the intercostal muscles and the ribs J Appl Physiol, June 1, 2007; 102(6): 2332 - 2337. [Abstract] [Full Text] [PDF]

				A. De Troyer and D. Leduc Effect of diaphragmatic contraction on the action of the canine parasternal intercostals J Appl Physiol, July 1, 2006; 101(1): 169 - 175. [Abstract] [Full Text] [PDF]

				D. Leduc and A. D. Troyer The effect of lung inflation on the inspiratory action of the canine parasternal intercostals J Appl Physiol, March 1, 2006; 100(3): 858 - 863. [Abstract] [Full Text] [PDF]

				A. De Troyer, P. A. Kirkwood, and T. A. Wilson Respiratory Action of the Intercostal Muscles Physiol Rev, April 1, 2005; 85(2): 717 - 756. [Abstract] [Full Text] [PDF]

				A. De Troyer and D. Leduc Effects of inflation on the coupling between the ribs and the lung in dogs J. Physiol., March 1, 2004; 555(2): 481 - 488. [Abstract] [Full Text] [PDF]

				P. Scillia, M. Cappello, and A. De Troyer Determinants of diaphragm motion in unilateral diaphragmatic paralysis J Appl Physiol, January 1, 2004; 96(1): 96 - 100. [Abstract] [Full Text] [PDF]