The parietal forms a major part of the cranium, covering large portions of the top, sides and back of the head. This is the point of articulation with the neck. The occipital is located at the lower rear of the head and forms the back and base of the skull. The frontal forms the top front of the head, the forehead, the brow ridges and the nasal cavity. The ethmoid forms part of the eye cavity. Then the separate cranial bones fuse together and remain that way throughout adulthood. In normal development, the cranial bones remain separate until about age two. The human cranium, which houses and protects the brain, is composed of six major bones: the ethmoid, frontal, occipital, parietal, sphenoid and temporal. The difference is that those abnormalities usually self correct, while craniosynostosis worsens if it is left untreated. An abnormal skull shape at birth is not always craniosynostosis and may be related to fetal head position or birth trauma. Synostosis of a particular suture alters the skull shape in a recognizable manner. The severity and type of deformity depends on which sutures close, the point in the development process that the closure occurred and the success or failure of the other sutures to allow for brain expansion. In some cases, the growth of the skull is restricted enough to cause increased pressure in the head and can lead to headaches, visual problems or developmental delays. The condition is usually apparent in infancy as an abnormal but characteristic head shape and, in some patients, abnormal facial features. Due to this closure, the baby develops an abnormally shaped skull because the bones do not expand normally with the growth of the brain. When the connective tissue between the adjacent bones is reduced to a narrow layer, these fibrous joints are now called sutures.Craniosynostosis is a congenital deformity of the infant skull that occurs when the fibrous joints between the bones of the skull (called cranial sutures) close prematurely. The fontanelles greatly decrease in width during the first year after birth as the skull bones enlarge. After birth, these expanded regions of connective tissue allow for rapid growth of the skull and enlargement of the brain. During birth, the fontanelles provide flexibility to the skull, allowing the bones to push closer together or to overlap slightly, thus aiding movement of the infant’s head through the birth canal. These broad areas of connective tissue are called fontanelles. In newborns and infants, the areas of connective tissue between the bones are much wider, especially in those areas on the top and sides of the skull that will become the sagittal, coronal, squamous, and lambdoid sutures. The joint between the mandible and the cranium, the temporomandibular joint, forms the only non-sutured joint in the skull. The fusion of the skull’s bones at birth is known as craniosynostosis. It is normal for many of the bones of the skull to remain unfused at birth. Cranial sutures are depicted with the frontal suture highlighted in blue. The suture is frequently convoluted, forming a tight union that prevents most movement between the bones.įrontal suture top view: Drawing of human baby skull seen from the top. In adults, the skull bones are closely opposed and fibrous connective tissue fills the narrow gap between the bones. The fibrous connective tissue found at a suture (to bind or sew) strongly unites the adjacent skull bones and thus helps to protect the brain and form the face. Sutures primarily visible from below the skull (norma basalis) or inside the skull include: Sagittal suture: along the midline, between parietal bones.Frontal suture / Metopic suture: between the two frontal bones, prior to the fusion of the two into a single bone.Sutures primarily visible from front of the skull (norma frontalis) or above the skull (norma verticalis) include: Squamosal suture: between the parietal and the temporal bone.Lambdoid suture: between the parietal, temporal, and occipital bones.Coronal suture: between the frontal and parietal bones.Sutures primarily visible from the side of the skull (norma lateralis) include: Most sutures are named for the bones they articulate, but some have special names of their own. \( \newcommand\)Ĭranial Sutures: Lateral view of skull showing the location of some of the cranial sutures.
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