Muscles can pull bones, but they can't push them back to the original position.
Bones shape our body and help us to stand up straight. A child's seesaw is an example of this type of lever. We get bigger and taller when our bones grow.
They are linked by cartilage, as in the spine. Bone-building continues throughout life, as a body constantly renews and reshapes the bones' living tissue. The walls of the heart's chambers are composed almost entirely of muscle fibers.
The soft bone marrow inside many of our bones is where most of the blood cells flowing through our bodies are made.