Most of the bones in the human body are present at birth, but there are exceptions. One notable example is the kneecap, or patella. This small, triangular bone resides in front of the knee and helps to protect it from impact. The patella forms later in life, around the age of three, as part of a process called ossification. This is when cartilage—a type of connective tissue—begins to harden and turn to bone. The patella is not the only bone that develops in this way; other bones, such as the lower jawbone and certain bones in the foot, also undergo ossification during childhood. As we grow older, our bones continue to change in response to our daily activities. For example, weight-bearing exercise can lead to increased bone density, while extended periods of immobilization can lead to bone loss. But no matter what our lifestyle, we all start out with a few bones yet to form.
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