Fact 2 of 10
2. The baby is born with more bones than the adult
An adult has 206 bones, but a newborn has nearly 300 bony pieces. Many of them are still cartilage and gradually fuse together during childhood and adolescence.
Bones that join together over time
At the beginning of life, much of the skeleton is cartilage, a tissue more flexible than bone. Little by little it is replaced by bone, in a process called ossification, and several separate pieces join into one.
The skull is the best-known example. In the baby, the bones of the head are not yet fused and leave soft gaps between them, the fontanelles, the familiar soft spot. This allows the head to adjust during birth and lets the brain grow quickly in the first year.
Other fusions happen much later. The hip bones, for example, start as separate pieces that join in adolescence, and some skeletal unions are not complete until after age 20.
The growth plates near the ends of long bones, such as the femur, also close at the end of adolescence. It is after this closure that a person stops growing in height.
Even after it has formed, the skeleton keeps renewing itself. Specialized cells break down small parts of the bone and others build new tissue in their place, and this cycle replaces much of the adult skeleton over roughly ten years.
Did you know? The kneecap, the bone at the front of the knee, is still cartilage in the newborn. It only begins to turn into bone between the ages of 3 and 6.
