All living organisms have certain characteristics (life functions) that distinguish them from non-living forms. The basic processes of life include organization, metabolism, responsiveness, movements, and reproduction. In humans, who represent the most complex form of life, there are additional requirements such as growth, differentiation, respiration, digestion, and excretion. All of these processes are interrelated. No part of the body, from the smallest cell to a complete body system, works in isolation. All function together, in fine-tuned balance, for the well being of the individual and to maintain life. Disease such as cancer and death represent a disruption of the balance in these processes.
Body functions are the physiological or psychological functions of body systems. The body’s functions are ultimately its cells’ functions. Survival is the body’s most important business. Survival depends on the body’s maintaining or restoring homeostasis, a state of relative constancy, of its internal environment.
The body’s ability to perform many of its functions changes gradually over the years. In general, the body performs its functions least well at both ends of life—in infancy and in old age. During childhood, body functions gradually become more and more efficient and effective. During late maturity and old age the opposite is true. They gradually become less and less efficient and effective.
Until then, our life functions will slowly terminated. And die we may come.