Answer
Fontanels are areas in the cranium where embryonic mesenchyme (unossified at birth) develops into dense connective tissue. Eventually the connective tissue is replaced by intramembranous bone. Sutures are the residual tissue between the cranial bones in the mature humans.
Work Step by Step
There is an unpaired anterior fontanel, and there is an unpaired posterior fontanel. There are also paired anterolateral and paired posterolateral fontanels. The paired anterolateral fontanels are bordered by the frontal, parietal, temporal and sphenoid skull bones. The paired anterior fontanels close about three months after birth. The unpaired anterior fontanel is the last to close-- about 22 months after birth
