Because the products of their labor are so personal, often developed for particular individuals or small groups, the rehabilitation engineer often works directly with the disabled individual. Systems physiology is the term used to describe that aspect of biomedical engineering in which engineering strategies, techniques and tools are used to gain a comprehensive and integrated understanding of the function of living organisms ranging from bacteria to humans. Modeling is used in the analysis of experimental data and in formulating mathematical descriptions of physiological events. In research, models are used predictively in designing new experiments to refine our knowledge. Living systems have highly regulated feedback control systems which can be examined in this way.
Examples are the biochemistry of metabolism and the control of limb movements.
Tissue engineering is an interdisciplinary field in which the principles of engineering and life sciences are applied toward the generation of biological substitutes aimed at the creation, preservation or restoration of lost organ function. This field is dedicated to the creation of new functional tissue. These specialty areas frequently depend on each other. Often the biomedical engineer who works in an applied field will use knowledge gathered by biomedical engineers working in more basic areas. For example, the design of an artificial hip is greatly aided by a biomechanical study of the hip.