What is the difference between woven bone and lamellar bone? What is the type of

Question

What is the difference between woven bone and lamellar bone? What is the type of bone that is intermediate between these two types called? What is the difference between fibrolamellar and lamellar-zonal bone? Address growth rate of bone (rate of deposition of osseous tissue) and vascularity? What does this have to do with the life-history of an animal (in this case, an endothermic duck and an ectothermic croc)? What is the significance of woven bone for animals that must grow to large size quickly? What is the significance for repair of damaged/diseased bone?

Explanation / Answer

The Woven (Primary) bone tissue is characterized by haphazard organisation of collagen fibers and is mechanically weak. Woven bone is produced when osteoblasts produce osteoid rapidly.

The Woven (primary) bone tissue is weaker, with a smaller number of randomly oriented collagen fibers, but forms quickly. It has been named due to woven appearance of fibrous matrix

Woven (primary) bone tissue has lower mineral content.

Woven (primary) bone tissue has higher proportion of osteocytes

The Woven (primary) bone tissue is basically either immature bone or pathologic bone. It not stress oriented. Compared to lamellar bone, woven bone has more osteocytes per unit of volume and higher rate of turnover. It is replaced in adults by the lamellar bone except in few places i.e. near sutures of flat bones of skull.

The Lamellar (secondary) bone tissue is secondary bone created by remodelling of woven bone.It has a regular parallel alignment of collagen into sheets (lamellae) and is mechanically strong. It is highly organized in concentric sheets with a much lower proportion of osteocytes to surrounding tissue. Lamellar bone is stronger and filled with many collagen fibers parallel to other fibers in the same layer osteons.

In cross-section, the fibers run in opposite directions in alternating layers. This kind of structural arrangement assists in the bone’s ability to resist torsion forces.

The fibro-lamellar bone speed and characteristics intermediate to woven and lamellar bone. Builds scaffolds quickly, then layer lamellar bone: alternating layer patterns. The fibro lamellar bone is always rich in primary osteons, set in a matrix of woven bone which is typically laid down rapidly. This type of bone is seen mainly in medium- to large-sized endotherms, and reflects their ability to reach such sizes more quickly than comparable ectotherms. The presence of fibro-lamellar compacta, without annuli and zones, in various dinosaurs is hence seen as evidence that dinosaurs were endotherms.

The lamellar-zonal bone bone laid down by accretion at the periosteal (external) surface shows a general coarsely lamellated texture, and vascular canals (for blood vessels) are often sparsely developed and sometimes lacking. Primary osteons, formed by inward growth of bone inside vascular canals, may be present or absent. This type of compacta is seen in bones which grow slowly or only to small sizes, and is the only type seen in most ectotherms. In ectotherms, lamellar-zonal bone may show a cyclical alternation of thin layers of dense bone, termed annuli, with thicker vascular layers known as zones.

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