Joining of Cranial Bones: Synostoses and Sutures
The joining of various parts of the skeleton to each other varies greatly according to their topography within the body. The most intensive connection of the skeletal parts can be found in the skull, in particular in the neurocranium. In the adult, the frontal bone is made up of one piece, where there were originally two frontal bones. The original suture between the frontal bones (fig. 3.5.) disappears completely. This osteoid connection is, therefore, called a synostosis. The connection with the parietal bones is the coronal suture. The anatomical construction of the sutures leads to a near immobilization of the bones of the skull with respect to each other. The morphological association that is expressed here can be characterized as a tendency towards convergence and immobility.
Joints that allow any free movement between the bones of the skull are not present in the neurocranium. The joints and articulating sections of bone that do occur in the head, such as the temporomandibular joint and the joints of the auricular bones, are derived from the branchial arches and are, in the restricted sense, not seen as part of the development of the cranium.