Sutures on the cranium are the locations where bones connect. When a fetus develops during pregnancy, the sutures are open and the bones far apart, held together by cartilage. This gives the cranium flexibility as the brain grows. As a person grows into adulthood and brain growth slows, bones come close enough together that they can touch. Some interlock like a zipper, and some are flat and overlap like tectonic plates. As adults age, the sutures often even fuse together. The major sutures are shown on the diagrams below, however, there are many more within the skull. Sometimes the metopic suture is present into adulthood; that is, a remnant suture that runs down the front of the frontal bone stemming from the early stages in human development.