fontanelle

A fontanelle is a membranous gap between the bones of the skull. In humans these soft spots on an infant's head allow the bony plates of the skull to flex during birth so that the head can pass through the birth canal. They are not permanent: ossification of the skull bones closes them over by about a child's second birthday, and the closures eventually become the sutures of the neurocranium. Besides the anterior and posterior fontanelles, two others are of anatomical interest, the mastoid fontanelle and the sphenoidal fontanelle. Six subordinate structures are recorded beneath this entry, matching the named gaps described in the developing skull, and the Latin form is given as fontanel.