Babies Are Born With More Bones Than Adults, But Why?

Compared to adults, babies actually have more bones. Why is this the case?

Bones Explained

Babies are born with roughly 300 bones in total. Each day, these bones grow and change in shape. On the other hand, adults have 206 bones that account for 15% of body weight. This means that babies have almost 100 more bones compared to adults.

While bones appear rigid and rough, they actually consist of calcium and living tissue. These get built up and discarded through the course of one's life.

The majority of bones consist of several tissue layers, namely the periosteum, compact bone, cancellous, and bone marrow. The periosteum is a thick membrane that can be found in the bone's outer surface, while the compact bone is the hard and smooth layer that is seen in a skeleton's bones. The cancellous tissue is sponge-like and is inside the compact bone, while the bone marrow is the bone's jelly-like core that produces blood cells.

Bone development happens in a process known as ossification. This typically starts during the eighth week of development of the embryo.

During birth, several bones of babies consist of cartilage, which is a tough but flexible connective tissue. Flexibility is crucial so that growing babies may curl up within the womb prior to being born. This also makes it easier for both the baby and the mother when the baby is due for birth.

Bone Fusing and Growth

As the baby develops and reaches childhood, much of the cartilage will get replaced with bone. However, there is also something else that takes place, which can shed light on why adults have a lesser number of bones compared to babies.

Several baby bones end up fusing with each other, decreasing the actual bone count. The space that separates two bone ends that fuse eventually also consists of cartilage. This bone fusing takes place all over the body.

The process of replacing cartilage with bone that is fused starts when small blood vessels, known as capillaries, bring blood rich in nutrients to the osteoblasts, which are bone-forming cells. These cells make bone that initially covers and then replaces cartilage.

Then, the growth of bones among children takes place at several bones' ends that have growth plates. The tissue growing within each plate determines the final bone's shape and size. When the growth of a person stops, these growth plates also close.

Compared to other parts of the skeleton of a child, growth plates are weaker. Because of this, they are more vulnerable to injuries and fractures.

Throughout this process, calcium plays a pivotal role in new bone tissue formation. The mineral can be found in both formula and breast milk.

When the person approaches early adulthood, bone growth and fusing stops. The bones of adults are light but strong. While these bones could appear unchanging and solid, they actually constantly undergo a process known as remodeling, which involves new bone tissue formation and older bone breakdown into calcium and other types of minerals that get released into the bloodstream. Such a process is called resorption. It is a healthy and normal part of bone function. However, for children, resorption is outpaced by new bone formation.

Generally, the process of bone fusion and growth is remarkable. To ensure bone health in the coming years, there are some things that can be done. These include ensuring that the child gets sufficient calcium, engages in weight-bearing exercises, and gets sufficient vitamin D.