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- Discussion:
    - cancellous or spongy bone is found at ends of long bones & makes up greater part of cuboidal bones;
    - its chemical composition and ultrastructure are identical to that of cortical bone;
    - cancellous bone is also formed in layers & is, therefore, lamellar bone;
    - one difference between cancellous and cortical bone is absence of haversian systems in former;
    - since cancellous bone is in the form of thin plates, its cells are never very far from surface,and their canalicular systems are therefore 
         adequate to supply nutrition;
    - thus, there is no need for the complicated haversian systems;
    - cancellous bone, like all other bone, is formed by osteoblasts that line the surface of small trabeculae;
    - cancellous bone of the body presents a tremendously large surface area that responds readily to physical and metabolic demands of body;
    - it is more active metabolically than compact bone & its remodeling rate is higher