Which of the following statement(s) is/are true concerning types of bone found in the human body?

b. Primary bone must be formed on existing surfaces

d. Secondary osteonal bone is the primary constituent of adult cortices

Two major types of bone are found in the human body: trabecular and cortical. Although the chemical, molecular and cellular components are similar, the organization of these components at the ultrastructural and microstructural level leads to significant differences in their mechanical and metabolic activities. The microstructural organization of bone can be classified into three types: primary bone, secondary bone, and woven bone. The most important characteristic of primary bone is that it must be formed on existing surfaces. The surfaces can be cartilaginous or preexisting bone. This bone is highly organized and exhibits excellent mechanical properties. Secondary osteonal bone is the primary constituent of adult cortices. The final microstructural type of bone is woven bone. Although the collagen matrices in lamellar and osteonal bone are precisely organized, providing maximal mechanical properties with minimal material, woven bone is composed of disorganized yet highly mineralized tissue and is expressed in the course of fracture or damage repair. It has the advantage of being quickly deposited but the disadvantage of significantly reduced mechanical properties when compared to a highly ordered primary and secondary bone.