Bone tissue composition

Robinson, R.A. Bone tissue composition and function. Johns Hopkins Med. J. 145, 10-24 (1979)... 

McCreadie, B.R. et al. (2006) Bone tissue compositional differences in women with and without osteoporotic fracture. Bone, 39 (6), 1190-1195. 

Bone is a porous tissue composite material containing a fluid phase, a calcified bone mineral, hydroxyapatite (HA), and organic components (mainly, collagen type). The variety of cellular and noncellular components consist of approximately 69% organic and 22% inorganic material and 9% water. The principal constiments of bone tissue are calcium (Ca ), phosphate (PO ), and hydroxyl (OH ) ions and calcium carbonate. There are smaller quantities of sodium, magnesium, and fluoride. The major compound, HA, has the formula Caio(P04)g(OH)2 in its unit cell. The porosity of bone includes membrane-lined capillary blood vessels, which function to transport nutrients and ions in bone, canaliculi, and the lacunae occupied in vivo by bone cells (osteoblasts), and the micropores present in the matrix. 

Bone is an extremely dense connective tissue that, in various shapes, constitutes the skeleton. Although it is one of the hardest structures in the body, bone maintains a degree of elasticity owing to its structure and composition. It possesses a hierarchical structure and, as most of the tissues, is nanostructured in fact, it is a nanoscaled composite of collagen (organic extracellular matrix) and hydroxycarbonate apatite, (HCA, bone mineral). This nanostructure is in intimate contact with the bone cells (several microns in size), which result (at the macroscopic level) in the bone tissue. Figure 12.2 shows the bone hierarchical ordering from the bone to the crystalline structure of HCA. 

In contrast to soft biologies, whose mechanical properties primarily depend upon the orientation of collagen fibers, the mechanical properties of mineralized tissues, or hard biologies, are more complicated. Factors such as density, mineral content, fat content, water content, and sample preservation and preparation play important roles in mechanical property determination. Specimen orientation also plays a key role, since most hard biologies such as bone are composite structures. For the most part, we will concentrate on the average properties of these materials and will relate these values to those of important, man-made replacement materials. 

An important caution is that any data reduction procedure that begins with extraction of principal components is based on the assumption that the data set consists of a small number of constituents that contribute to the measured spectrum at any point in proportion to their composition at that point. These methods cannot be used if that assumption is not correct. For example, mechanical loading of bone tissue causes wave number and intensity shifts in both mineral and matrix bands. While the shifts are not always linear with Appl. load, they do vary continuously. 

Rezwan K, Chen QZ, Blaker JJ, Boccaccini AR (2006) Biodegradable and bioactive porous polymer/inorganic composite scaffolds for bone tissue engineering. Biomaterials 27(18) 3413—3431... 

There are 32 teeth and over 200 bones in an adult human, each a separate organ with its own essential role. These organs are composed of mineralized tissues, composites of bioorganic, and mineral that record the chemistry of what has been ingested, i.e., the C4 or C3 characteristics of the diet, as well as the overabundance of certain, perhaps hazardous cations, e.g., copper (Pyatt and Grattan, 2001), or shortfall of essential elements, i.e., calcium, that may lead to rickets, usually expressed in the abnormal appearance and function of the long bones. 

The results of animal tests using rats, rabbits, and dogs have demonstrated high biocompatibility and high osteoconductivity. Moreover, the most impressive bone tissue reaction of the HAp/Col composites is incorporation of the composites into the bone-remodeling process, that is, they are resorbed by osteoclastic cells. ... 

Lukashi, H. C. (1993). Soft tissue composition and bone minera status Evaluation by dual-energy X-ray absorptiometry. /. Nufr. 123,438-443. 

Using a similar procedure, a composite material for tissue engineering applications composed of HA and carboxymethylchitosan was obtained by a coprecipitation method. In vitro tests exhibited a great potential of this class of materials for bone tissue-engineering applications.79... 

If a scaffold is transplanted, the rate of biodegradability is important to ensure that the scaffold remains to support a transplant until a natural ECM replaces it. The biodegradation or resorption rate is a function of the scaffold composition, structure, and the mechanical load present at the site of transplantation. The necessary rate at which the scaffold is degraded varies according to the tissue type. For example, slow degradation is allowable in bone tissue, whereas in other tissues chronic inflammation may occur if the rate is too low.f It is important that the degradation by-products are nontoxic to the body. 

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