Coronary arteries in infants up to the age of ten years. I. Chronology of adaptive intimal changes.

In the coronary arteries of old fetuses the presence of musculo-elastic and elastic hyperplastic layers was firstly detected in the branching pads of aortic ostia and the emergence of the left anterior descending branch. These layers appeared constantly more developed in the left than in the right coronary bed. During the first six months of the extrauterine life the coalescence of pads revealed a passage from localized to diffuse adaptive changes in the main branching sites and in their immediate vicinity. Then, in the first decade of life, a progressive extension of the musculo-elastic and elastic hyperplastic layers was observed, leading to the well known aspect of diffuse intimal thickening.