Bone is made up of collagen, a protein responsible for the tensile strength of bone, and minerals such as calcium which hardens the bony framework.
The human skeleton has two different forms of bone.
- Compact bone is the hard outer shell of bone. The bone is packed together into rows of rod-like cylinders to make this layer strong, hard, and smooth looking.
- Spongy bone is the inner part of the bone and it is more delicate-looking than the outer bone. This bone has a honeycomb appearance formed by vertical and horizontal bars called trabeculae.
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