Final answer:
Frontal sutures are present in newborns and infants but fuse by the age of eight, while other sutures allow brain and skull growth. Premature closure of these sutures can lead to craniosynostosis, causing skull deformities and affecting brain development.
Step-by-step explanation:
Frontal sutures are present in newborns and infants but typically fuse to form a single bone by around eight years of age. Other sutures in the skull, such as the sagittal, coronal, squamous, and lambdoid sutures, are important for skull growth and brain development post-birth. Conditions like craniosynostosis, where one or more of these other sutures close prematurely, result in abnormal skull growth and can impede brain development. Complex craniosynostosis involves the fusion of several sutures, leading to more severe skull deformities and potentially affecting normal brain growth.