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A Description Of The Biology Of Bone

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Chapter 2

Background

2.1 Introduction

Chapter 2 will describe the essential background information needed to understand this

thesis project. A description of the biology of bone will be provided first and its focus

will be limited to femurs and tibiae, since those are the structures we have used

throughout this project. As well, we will briefly describe the analysis techniques that are

currently used to evaluate bones. Furthermore the theory behind the used technique and

instrumentation will be addressed. Previous bone studies using transcutaneous in vivo

Raman spectroscopy will also be described, as well as the differences between them and

the present thesis project.

2.2 Bone Structure and Composition

Bones
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12 Both the cortical and

trabecular structures provide ions like calcium phosphate, phosphorous, sodium and

magnesium that are basic to maintain the homeostasis of the bone.

Figure 1. Hierarchical structure of bone. Cotical bone is made of osteons (10-500 µm). Osteons are composed of concentric lamella (3-7 µm) and a Haversian cannal. A lamella is composed of mineralized collagen fibers, which are made up of collagen fibrils (0.5 µm each). A fibril is made up of collagen molecules and apatite nano-crystals.11

The three major components of bone tissues are: type I collagen, water and dahllite

crystals. 13 Dahllites are plate-shaped carbonated apatite crystals, which have “small but

significant amounts of impurities such as HPO4, Na, Mg, citrate, carbonate, K”. 14,15 The

apatite crystal lattice is then responsible for the degree of mineralization in bone tissue.

Type I collagen is the primary matrix component and its molecules are secreted by

Cortical bone

Osteons

Haversian canal

Concentric lamella

Mineralized collagen fibrils

Collagen molecule

Apatite nanocrystals 6 osteoblasts, these molecules will then arrange into collagen fibrils and subsequently to

collagen fibers, which are the basis to lamellae.

Type I collagen despite being the primary protein is not the only one present in

bone tissue, which also contains non-collagenous proteins.
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