The Haversion system is evidence of bone remodeling. See PJH for adult bone structure. Haversian systems in a fossilized dinosaur bone . Since in modern vertebrates only warm blooded adults form Haversian systems, their presence in the fossil has been used to argue that dinosaurs were warm blooded. Slides 21 and 23-27 are from the same preparation.
Cartilage always arises from mesenchymal condensations.
This tissue is very uniform because cartilage contains only chondrocytes and cartilage matrix. No blood vessels or nerves in cartilage. Cartilage cells, chondrocytes, can divide within their lacunae and this produces cartilage can grow because the matrix is nonmineralized and deformable. This is called interstitial growth. Bone always grows from the surface, appositionally, since the mineralized non-deformable matrix does not allow growth from within.