Biomedical Engineering Bridging Medicine and Technology

Prelude

Our bodies appear, from the outside, to be solid masses that are slow to change but, just beneath the surface, the body's fluids are in constant motion. Blood moves at high velocity throughout the body within an interconnected and highly branched network of vessels (Figure 8.1). The human circulatory system is responsible for the movement of fluid, and therefore the vital nutrients contained in the fluid, throughout the body.

The purpose of the circulatory system is a familiar one to engineers and bakers; it provides mixing, and good mixing is an essential element of many successful enterprises. Cakes are made from flour, eggs, sugar, and milk (among other things); your birthday will be ruined (or at least a bit tarnished) if the chef does not mix these ingredients well. But why must humans be mixed? Mixing exposes cells throughout the body to oxygen and other nutrients, while simultaneously providing a pathway for removal of waste products. It is the circulatory system that enables us to grow large, so that we have inner regions that are separated from the atmospheric oxygen that all cells need for energy (Figure 8.2).

Circulation of fluids is the function of the cardiovascular system. The human cardiovascular system is composed of three separate organs: The heart serves as a pump, the vasculature serves as the plumbing, and the blood is the circulated fluid. Failure in any of these organs can result in failure of the system, so diseases of the cardiovascular system have grave consequences.

Biomedical engineers have made contributions to almost every area of cardiovascular health, including construction of artificial hearts and heart valves (see Chapter 15), understanding of the flow properties of blood, and mathematical modeling of the microcirculation. In fact, some of the most important work in understanding the special blood vessels that develop in tumors has been done by biomedical engineers (Figure 8.3).