Changes in Structural Components of Human Body from Six Lunar Months to Maturity

The changes of the various structural components of the human body in development are well illustrated by volumetric histograms. These are shown in Figs. 1 and 2. They are based upon data collected in this laboratory as well as a series of records collated from the literature.

In this presentation the structural components of the body considered are: skin and superficial fat (paniculus adiposus), the visceral mass (including the heart), the nervous tissues (of both the peripheral and the central nervous systems), the voluntary musculature, and the fresh Iigamentous skeleton.

The periods represented are: 6 lunar or fetal months, birth, and full maturity. Both sexes are included in each of the periods.

Figure 1 illustrates the differences in composition of the body at 6 lunar months and at birth. During this interval the net weight of the body increases approximately five-fold, from 500 to 2500 g.

The relative changes in the distribution of the body components are: the skin and superficial fat increase from about one-sixth to over one-fourth of the body mass. The nervous tissue component and the skeletal component both show a marked relative decrease. The visceral and the voluntary muscle components remain almost constant.

Fig. 2 shows the changes in components between birth and maturity. During this interval the net body weight increases almost twenty-fold. The postnatal changes in the relative distribution of components consist of: a marked increase in the voluntary muscle from about one-fourth to over two-fifths of the body mass. But the visceral component decreases from about one-sixth to about one-tenth of the body mass; and the nervous tissue component from about one-seventh to about one-thirtieth. The skin and superficial fat component and the component of the skeleton remain practically unchanged.