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Lateral muscles of the thoracic ...


The three inner layers of the four-layered lateral muscle wall (the outermost muscle layer, the serratus anterior muscle, migrates onto the superior limb and is covered in that section of the program) form the thin muscle sheets between adjacent ribs that are functionally related to the diaphragm as important muscles of respiration. Activation of these muscles not only stiffens the thoracic wall, but assists in increasing or decreasing the volume of the thoracic cage to decrease the pressure for inspiration and increase thoracic pressure for expiration of air. The dome-like diaphragm, is a complex muscle sheet separating the thoracic cavity from the abdominal cavity, part of this sheet develops from the internal aspect of the body wall. The fibers of this dome-like muscle radiate like the spokes of a wheel, from the bottom of the rib cage and lumbar vertebral column, into a central tendon in the center of the muscular sheet. The diaphragm contains three openings that allow the inferior vena cava, the aorta, and the esophagus to pass from the thorax to the abdomen. The inferior vena cava passes through the central tendon of the diaphragm, the esophagus traverses the esophageal hiatus in the muscular portion of the diaphragm where it is surrounded by the muscular diaphragmatic crura, and the aorta passes behind the posterior edge of the diaphragm against the lumbar vertebral column.

Muscles Included

Diaphragm, Transversus thoracis, Subcostal, Innermost intercostal, Internal intercostal, External intercostal, Serratus posterior inferior, and Serratus posterior superior.


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