[The structure and mechanical properties of the human pulmonary trunk and its valves]

The histological structure and mechanical properties of the pulmonary trunk and its valves were studied in 35 complexes of the pulmonary artery of man. The valvular apparatus of the pulmonary trunk is formed by anatomical elements with different morphological structures. In it there are elements which might be considered from standpoints of biomechanics as membranous (pulmonary trunk, sinuses, cusps) and shaft (fibrous ring, commissural shafts, arcuate crests) elements, the commissural shafts representing a combination of structures forming a closed spatial inter-related construction--a natural elastic framework of the pulmonary trunk root and the sheath elements are morphologically interrelated and fixed on this framework. The mechanical properties of these shaft elements are formed not only at the expense of inclusion of other formations in their structure but also at the expense of changes in the density of distribution and spatial orientation of main carrier structures of sheath elements attached to them. So, the strength and rigidity of the fibrous ring were associated not only with the presence of collagenous fibers and chondroid tissue n it, but also with the regular arrangement of collagenous fibers coming to it from the sinus. Similarly, the strength of arcuate crests was in many respects dependent on dense arrangement of longitudinally oriented smooth muscles. The amount of smooth muscles in the pulmonary trunk was 1.3 and 2 times higher than that of collagenous and elastic structures which allows the pulmonary trunk of man to be referred to arteries of muscular or mixed type. It points to the necessity to take into account the influence of muscle tone on mechanical behavior of the pulmonary trunk under physiological exercise.