Comparison of the growth of the tunica media of the ascending aorta, aortic isthmus and descending aorta in infants and children.

This study concerns the normal histological growth of the aorta in infants and children. We measured, in post mortem material consisting of 69 hearts and great vessels of infants and children who died from non-vascular diseases, the internal diameters of the ascending aorta, aortic isthmus and descending aorta together with the thickness of the tunica media and the packing density of its elastic fibres. Age range was from 27 weeks of gestational age up to 10 years after birth. The growth of the tunica media of the ascending aorta was, in part, different from that of the aortic isthmus and descending aorta. Notwithstanding an increase in the thickness of the tunica media parallelling, in all three parts of the aorta, an increase in their internal diameters, the packing density of the elastic fibres of the tunica media of the aortic isthmus and of the descending aorta showed no tendency to increase with age. However, the packing density of the elastic fibres of the ascending aorta showed a continuing increase with age parallelling the increase of the internal diameter. This can probably be better explained as a result of functional difference than as a result of different embryological origin.