Final answer:
Fontanelles, known as 'soft spots,' are regions of fibrous connective tissue in a newborn's skull that enable the bones to move during birth and allow for skull growth post-birth, closing fully by around age 2.
Step-by-step explanation:
The incomplete areas of skull bone formation in newborns are known as fontanelles, often referred to as "soft spots". These broad areas consist of fibrous connective tissue that connect the braincase bones of the skull prior to and shortly after birth. The presence of fontanelles allows the skull plates to move and overlap, facilitating the baby's passage through the birth canal. Post-birth, they permit the continuous growth of the skull as the brain increases in size. The fontanelles eventually close as the process of intramembranous ossification completes, which usually occurs by the time the child is around 2 years old.