Correlation of types of cortical grain structure with architectural features of the human skull

Seven grain-form relationships, as indicated by the split-line patterns, are recognized in the cortical bone of the adult human skull: (1) random pattern of braincase, (2) planes and (3) ridges with elongated grain, (4) troughs with transverse grain, (5) concavities with circular grain, (6) edges, and (7) spines. Concavities may show superimposed trough or ridge structure, and troughs may be marked by localized ridges and planes. That is, trough patterns are dominant over concavity patterns, and ridge patterns are dominant over both trough and concavity patterns. Finally, there are a few small cranial areas that are random distributions in some skulls and planes in others; the skull vault proper, however, except for the forehead region and internal sagittal markings, has a random pattern throughout. The mechanical significance of the various patterns and the areas on which they are found are discussed and explained on the basis of principles of mechanics and architecture. The form-texture relationships are discussed as architectural features of the skull, and their adequacy and limitations are analyzed in terms of their reaction to force systems and their proneness to fracture.