I was a little surprised one afternoon during a dissecting class by what a colleague said as he mused out loud. He was wondering why it was that arteries closer to the heart had more elastic tissue in their walls than those further away which had more muscle fibres in their walls. It was clear from what he was saying that he thought that some sort of predetermined pattern was laid down deliberately in embryo. His was a quite static view. He did not take into account the pressure differences within the arterial tree and the different stimulatory effects these might have on the cells in the arterial walls. One might envisage, a higher pressure (closer to the heart) stimulating greater elastic fibre production at the expense of muscle fibres - and vice versa.
I was told by a medical student in one such dissecting class that, in coronary bypass surgery, grafted veins become like arteries after the operation due to the arterial pressures they experience. I have not been able to find convincing support for this assertion, although there is evidence that their walls do thicken in response to these pressures. I cannot find evidence that grafted veins become arteries per se. However, the fact that they do change illustrates the dynamic nature of the structures of the body and how we should be careful never to overlook that fact.
