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Although the skull appears to be one large bone, there are actually several major bones that are connected together. The major bones that compose the skull of a newborn include the following:
2 frontal bones
2 parietal bones
1 occipital bone
These bony plates cover the brain and are held together by fibrous material called sutures.
Some sutures extend to the forehead, while others extend to the sides and back of the skull. One suture in the middle of the skull extends from the front of the head to the back. The major sutures of the skull include the following:
Metopic suture. This extends from the top of the head down the middle of the forehead, toward the nose. The two frontal bone plates meet at the metopic suture.
Coronal suture. This extends from ear to ear. Each frontal bone plate meets with a parietal bone plate at the coronal suture.
Sagittal suture. This extends from the front of the head to the back, down the middle of the top of the head. The two parietal bone plates meet at the sagittal suture.
Lambdoid suture. This extends across the back of the head. Each parietal bone plate meets the occipital bone plate at the lambdoid suture.
Sutures allow the bones to move during the birth process. They act like an expansion joint, allowing the bone to enlarge evenly as the brain grows and the skull expands, resulting in a symmetrically shaped head. However, if any of the sutures close too early (fuse prematurely), there may be no growth in that area. This may force growth to occur in another area or direction, resulting in an abnormal head shape.
There are two fontanelles (the space between the bones of an infant's skull where the sutures intersect) that are covered by tough membranes. The fontanelles include:
Anterior fontanelle (also called soft spot). This is the junction where the two frontal and two parietal bones meet. The anterior fontanelle remains soft until about 2 years of age.
Posterior fontanelle. This is the junction of the two parietal bones and the occipital bone. The posterior fontanelle usually closes first, before the anterior fontanelle, during the first several months of an infant's life.