Chemical analysis of human foetal skull bones

Abstract

Chemical analysis of the frontal and parietal bones of the human fetus showed an increase in the proportions of Ca and carbonate as the fetus approached maturity, but no such increase in P and collagen. The mean proportional increase per dry weight of bone per week was 0.04% for Ca and 0.05% for carbonate. The inorganic chemical composition of growing membrane bone, as exemplified by the fetal parietal and frontal bones, may consist of a mixture of apatite, brushite and CaCO3 or of a mixture of calcium phosphate, CaCO3 and small amounts of other Ca salts. It is impossible, from the results obtained here, to indicate which is the more likely chemical arrangement. A probable increase in the proportion of CaCO3 in the skull bones as the fetus grows may be a factor in the increased "hardness" of the head associated with fetal maturity.