The composition of body tissues (II). Fetus to young adult.

The composition of body tissues is a function of the age, nutrition, state of health and physical activity of the individual. In this paper, the effects of age on the composition of healthy tissues are reviewed. Eleven soft tissues (adipose tissue, blood--whole, brain--whole, heart, kidney, liver, lung, muscle--skeletal, placenta, skin and spleen) and cortical bone are considered. Elemental compositions, mass and electron densities are tabulated for the tissues, as a function of age, from fetus to young adult. Although the compositions given here are predominantly for healthy tissues, reported changes because of dietary influences are briefly discussed.