Biomedical Engineering Reference
In-Depth Information
Figure 3
. Example of a modern prosthetic leg from Otto Bock Healthcare (85).
traction of a muscle, the filtration of a kidney, or the metabolic behavior of a
liver. Cells exist connected by a scaffold of solid and fluid. The solid is mostly
extracellular matrix (ECM) and the fluid is mainly blood (of course, blood con-
tains cells that have their own functions), while other solids and fluids exist in
smaller quantities. In some tissues the volume and mass of the scaffold greatly
exceeds that of the cells; in structural tissues such as blood vessels, heart valves,
and bone, the scaffold provides the main functionality and the cells mostly serve
to maintain the scaffold. Signals are molecules that communicate with the cells,
and that the cells use to communicate with each other. Some signals are soluble
and are transported between cells by fluid, and other signals are insoluble
and may be attached to the surface of a cell or the scaffold. Nutrients are mole-
cules needed to sustain the cell or are produced by the cell. The circulatory sys-
tem exists to transport nutrients, especially oxygen, to and from all of the cells in
the body.
