To distribute stress uniformly, trees add wood at the heaviest load points. Bones remove material from areas where it isn't needed to lighten skeletal frameworks.
Their skeletal structure is extremely flexible, as it is made of cartilaginous material rather than hard bone.
其骨骼构造非常柔韧，因为他们没有硬骨，只有软骨。
3
BACKGROUND: Carbonated hydroxyapatite cement is a new type material for skeletal repair and hydroxyapatites have been applied in the clinical treatment of skeletal defect.