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Triangularis sterni: a primary muscle of breathing in the dog

Journal of Applied Physiology 60(1): 14-21

Triangularis sterni: a primary muscle of breathing in the dog

The isolated action, pattern of neural activation, and mechanical contribution to eupnea of the triangularis sterni (transversus thoracis) muscle were studied in supine anesthetized dogs. Linear displacement transducers were used to measure the axial displacements of the ribs and sternum. Tetanic stimulation of the triangularis sterni in the apneic animal caused a marked caudal displacement of the ribs, a moderate cranial displacement of the sternum, and a decrease in lung volume. During quiet breathing, there was invariably a rhythmic activation of the muscle in phase with expiration that was independent of the presence or absence of activity in the abdominal and internal interosseous intercostal muscles. This phasic expiratory activity in the triangularis sterni was of large amplitude and caused the ribs to be more caudal and the sternum to be more cranial during the spontaneous expiratory pause than during relaxation. Additional studies on awake animals showed that rhythmic activation of the triangularis sterni occurs in all body positions and is not caused by anesthesia. These findings indicate that expiration in the dog is not a passive process and that the end-expiratory volume of the rib cage is not determined by an equilibrium of static forces alone. Rather, it is actively determined and maintained below its relaxation volume by contraction of the triangularis sterni throughout expiration. The use of this muscle is likely to facilitate inspiration by increasing the length of the parasternal intercostals and taking on a portion of their work.

Accession: 006840714

PMID: 3944024

Related references

Estenne M.; Ninane V.; D.T.oyer A., 1988: Effect of posture on triangularis sterni muscle use during breathing in man. FASEB Journal 2(5): ABSTRACT 6991

D.T.oyer A.; Ninane V., 1985: The triangularis sterni a primary muscle of inspiration in the dog. Federation Proceedings 44(4): 1003

Ninane, V.; Decramer, M.; D.T.oyer, A., 1986: Coupling between triangularis sterni and parasternals during breathing in dogs. The purpose of the present studies was to assess the functional coupling between the parasternal intercostals and the triangularis sterni (transversus thoracis) muscles during resting breathing, and we measured the electrical activity and the resp...

D.T.oyer, A.; Ninane, V.; Gilmartin, J.J.; Lemerre, C.; Estenne, M., 1987: Triangularis sterni muscle use in supine humans. The electrical activity of the triangularis sterni (transversus thoracic) muscle was studied in supine humans during resting breathing and a variety of respiratory and nonrespiratory maneuvers known to bring the abdominal muscles into action. Twel...

Van Lunteren E.; Haxhiu M.A.; Cherniack N.S.; Arnold J.S., 1988: Role of the triangularis sterni muscle during coughing in dogs. Clinical Research 36(3): 508A

Van Lunteren E., 1991: Contractile and endurance properties of feline triangularis sterni muscle. The triangularis sterni muscle has recently been found to play an active role in the modulation of airflow during expiration in several species; furthermore its electrical activity is influenced by many chemical and mechanical stimuli which influe...

Estenne M.; Ninane V.; D.T.oyer A., 1988: Triangularis sterni muscle use during eupnea in humans effect of posture. The electromyograms of the triangularis sterni (transversus thoracis), of the abdominal external oblique, and of the deeper abdominal muscle layer (internal oblique or transversus abdominis) were recorded with concentric needle electrodes in twent...

Mcardle J.J.; Angaut Petit D.; Mallart A.; Bournaud R.; Faille L.; Brigant J.L., 1981: Advantages of the triangularis sterni muscle of the mouse for investigations of synaptic phenomena. The triangularis sterni muscle (TS) of the mouse is a thin trapezoidal sheet of fibers in which individual neuromuscular junctions are easily observed with Nomarski optics. Microelectrodes are readily positioned to accurately record various synapt...

Carlson, C.George.; Gueorguiev, A.; Roshek, D.M.; Ashmore, R.; Chu, J.S.; Anderson, J.E., 2003: Extrajunctional resting Ca2+ influx is not increased in a severely dystrophic expiratory muscle (triangularis sterni) of the mdx mouse. Freshly isolated adult mdx and nondystrophic (C57B110SnJ) muscle fibers were used to examine the potential role of resting Ca2+ influx in the pathogenesis of Duchenne and related dystrophies. Microfluorimetric determinations of resting divalent ca...

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