Medicine is one of the branches of scientific research in which numerical simulation can give a great support. In particular, a well mature branch like computational fluid dynamics (CFD) can provide a substantial help for the understanding of several pathologies of the cardiovascular system. The local behavior of blood flow may affect substantially the on-rise of such pathologies: a remarkable instance is atherosclerosis, which is unfortunately largely widespread in Western Countries. An accurate fluid dynamics analysis can better enlight these mechanisms, and CFD becomes necessary since physical data from ``in vivo'' measures are troublesome to obtain. Moreover, allowing completely controlled simulations, CFD can eventually provide a useful paradigm for clinical practice, for instance suggesting optimal strategy for a surgeric operation. par However, the study of biological systems is a difficult task not only from the numerical viewpoint, but also in the modeling phase. Indeed, different systems interact each other at mechanical or biochemical level. Therefore, making a hierarchy of simplifications in the models considered is almost always mandatory. These notes illustrate some specific features of the blood flow problem, in the case of ``large'' vessels, where the atherosclerotic plaques are localized. In particular, the interaction between blood and compliant vessel walls is of upmost interest. The purpose is to review shortly the existing literature on the field (limitedly to the most genuine mathematical aspects) and mention a first contribution from our side to the modeling of blood-wall interaction and its numerical simulation.