Comparison of medial growth of human thoracic and abdominal aortas.

Recent morphologic studies of adult mammalian thoracic and abdominal aortic segments have shown that the adult human abdominal aorta deviates significantly from the usual pattern of medial lamellar architecture. In the present study medial growth of these two aortic segments from prenatal life to adulthood was compared in terms of medial architecture and calculated tangential tension levels. During prenatal life, these parameters were very similar in the two segments. However, the postnatal increase in the medial thickness of the thoracic segment was due mainly to the addition of lamellar units which increased in number from 35 to 56; only a minor contribution was made by increased thickness of each unit which changed from 0.012 to 0.017 mm. The converse was true for the abdominal segment; the number of lamellar units increased only from 25 to 28, but lamellar unit thickness increased strikingly from 0.012 to 0.026 mm. Calculated wall stress was similar in the two segments throughout growth, but tension per lamellar unit became disparate in the segments during the first decade of life, culminating in unusually elevated values in the adult human abdominal aortic media. ADDITIONAL