Woven or lamellar

Two types of bone can be identified microscopically according to the pattern of collagen forming the osteoid (collagenous support tissue of type I collagen embedded in glycosaminoglycan gel):

1) Woven bone characterised by haphazard organisation of collagen fibers and is mechanically weak, and

2) Lamellar bone which has a regular parallel alignment of collagen into sheets (lamellae) and is mechanically strong.

Woven bone is produced when osteoblasts produce osteoid rapidly which occurs initially in all fetal bones (but is later replaced by more resilient lamellar bone). In adults woven bone is created after fractures or in Paget's disease. Woven bone is weaker, with a smaller number of randomly oriented collagen fibers, but forms quickly; it is for this appearance of the fibrous matrix that the bone is termed woven. It is soon replaced by lamellar bone, which is highly organized in concentric sheets with a much lower proportion of osteocytes to surrounding tissue. Lamellar bone, which makes its first appearance in the fetus during the third trimester,^[10] is stronger and filled with many collagen fibers parallel to other fibers in the same layer (these parallel columns are called osteons). In cross-section, the fibers run in opposite directions in alternating layers, much like in plywood, assisting in the bone's ability to resist torsion forces. After a fracture, woven bone forms initially and is gradually replaced by lamellar bone during a process known as "bony substitution."

These terms are histologic, in that a microscope is necessary to differentiate between the two.