Functional Relations Among Cells and Fibers of the Aortic Media: Microanatomic and Biosynthetic Findings
Decreasing distensibility of the aorta with increasing intraluminal pressure was first observed nearly a century ago. Investigators have since used increasingly standardized preparations and refined measuring methods to provide precise quantitative data with regard to the relative roles of elastin, collagen, and smooth muscle cells in determining the shape of the distensibility curves under both static and dynamic conditions. Morphologic studies and measurements of rabbit aortas fixed while distended over a range of pressures permitted us to develop an initial three-dimensional picture of aortic medial structural organization consistent with its static mechanical properties. At distending pressures well below diastolic values, elastin fibers are wavy, collagen fibers seem to be distributed randomly, and cells appear to be disposed more or less radially between the wavy elastin lamellae. With increasing pressure, a different pattern emerged as the fibers straightened. At physiologic pressures, elastin appeared as a more or less circumferentially oriented network whose component fibers condensed at regular intervals across the wall to form relatively compact straight lamellae. Collagen fibers appeared to be oriented circumferentially among the elastin fibers.
KeywordsSmooth Muscle Cell Basal Lamina Scanning Electron Micro Pulmonary Trunk Elastin Fiber
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