Fontanelle is

• A. A protective layer around the brain.
• B. A blood vessel that supplies the brain.
• C. A membranous sac surrounding the brain.
• D. A soft spot where bones meet.

Answer: (D)

Fontanelle is a soft spot on an infant’s skull where the bones have not yet fused. This area allows the skull to be flexible during birth and provides room for rapid brain growth in infancy. It isn’t a protective layer around the brain (that would be the meninges), nor a blood vessel, nor a membranous sac surrounding the brain. The soft spot will gradually close as the skull bones fuse, with the anterior fontanelle typically remaining open until about 18 to 24 months of age. Clinically, you can assess fontanelles to gauge hydration and intracranial pressure in infants; a sunken fontanelle suggests dehydration, while a bulging, tense fontanelle can indicate increased intracranial pressure.