Cortical bones

A bone is classified according to shape as flat, long, short, or irregular. A living bone consists of three layers the periosteum, the hard cortical bone, and the bone marrow or cancellous bone. The periosteum is a thin coUagenous layer, filled with nerves and blood vessels, that suppHes nutrients and removes cell wastes. Because of the extensive nerve supply, normal periosteum is very sensitive. When a bone is broken, the injured nerves send electrochemical neural messages relaying pain to the brain. 

The process of aging reduces bone size and strength. Thinning and resorption occur in the canceUous bone. Also, cortical bone resorbs and bone shrinks in diameter and thickness. The older the person, the more fragile the bone. 

Diagenesis of the inorganic phase of cortical bone. In Price, T.D., ed.. Bone Chemistry and Past Behaviour. Cambridge, Cambridge University Press 211-229. 

The Snake Hill sample was chosen for this research because the cortical bone had been buried for a known length of time in relatively homogeneous... 

Rudder AM, Leenders H, and van Blitterswijk CA. Interface reactions to PEO/PBT copolymers (Polyactive) after implantation in cortical bone. J Biomed Mater Res, 1994, 28, 141-151. 

The geometry and structure of a bone consist of a mineralised tissue populated with cells. This bone tissue has two distinct structural forms dense cortical and lattice-like cancellous bone, see Figure 7.2(a). Cortical bone is a nearly transversely isotropic material, made up of osteons, longitudinal cylinders of bone centred around blood vessels. Cancellous bone is an orthotropic material, with a porous architecture formed by individual struts or trabeculae. This high surface area structure represents only 20 per cent of the skeletal mass but has 50 per cent of the metabolic activity. The density of cancellous bone varies significantly, and its mechanical behaviour is influenced by density and architecture. The elastic modulus and strength of both tissue structures are functions of the apparent density. 

GAO Y H and YAMAGUCHI M (1999c) Anabolic effect of daidzein on cortical bone in tissue culture Comparison with genistein effect. Mol Cell Biochem 194, 93-8. 

The human skeleton consists of both cortical and trabecular bone. Cortical bone is dense and compact and is responsible for much of bone strength. It is the most common type of... 

Skeletal deposition is assumed to distribute into two pools 50% goes to the trabecular bone surface and 50% to the cortical bone surface. A first order rate coefficient for elimination of americium from liver to plasma is assumed to be 0.0019 day 1 (half-time, 365 days). 

Distribution. Bone constitutes the largest fraction of the deposited body burden of americium in all mammalian species that have been studied. The mechanisms by which americium is taken up and retained in bone are only partially understood. The distribution of americium in bone initially is confined to bone surfaces, including endosteal and periosteal surfaces, and adjacent to vascular canals in cortical bone (Polig 1976 Priest et al. 1983, 1995 Schlenker et al. 1989). Deposition appears to be favored at sites of active... 

Chipperfield AR, Taylor DM. 1972. The binding of thorium(IV), plutonium(IV), americium(III) and curium(III) to the constituents of bovine cortical bone in vitro. Radiat Res 51 15-30. 

Herring GM, Vaughn J, Williamson M. 1962. Preliminary report on the site of localization and possible binding agent for yttrium, americium and plutonium in cortical bone. Health Phys 8 717-724. 

Among the oldest women with impaired calcium balance a high caffeine intake may predispose to cortical bone loss. However, effects were age and site specific and after... 

Diffusible plasma / tissue / extravascular fluid / red blood cells / bound plasma (x103) / urinary bladder / urinary path /small intestine /trabecular bone surface / cortical bone surface / liver, rapid turnover rate / other kidney (x103) / other soft tissues, rapid turnover rate / other soft tissues, moderate turnover rate (x10) / other soft tissues, slow turnover rate (x102) / brain (x103) / sweat Bone / tissue (x103) 1,000 297-480 500-800 19-30 25-40 7.4-12.0 58-132 71-384 50-80 350-400 103-178 100-178 124-200 188-763 4.3-7.0... 

The toxicokinetics of lead in children appears to be similar to that in adults, with the exception of the higher absorption of ingested lead in children. Most of the lead body burden in both children and adults is in bone a slightly large fraction of the body burden in adults resides in bone (Barry 1975). The difference may reflect the larger amount of trabecular bone and bone turnover during growth trabecular bone has a shorter retention halftime for lead than does cortical bone (See Section 2.3.3 for details). 

Gong JK, Arnold JS, Cohn SH. 1964. Composition of trabecular and cortical bone. AnatRec 149 325-331. 

Rosen JF, Markowitz ME, Jenks ST, et al. 1987. L-X-ray fluorescence (XRF) A rapid assessment of cortical bone lead (Pb) in Pb-toxic children. Pedia Res 21 287A. 

The combination of bioactive ceramic particles and a polymer matrix gives bioactive materials which show mechanical properties analogous to those of human cortical bone. However, the bioactivity is not so high because the filler content is limited due to the brittleness, and the weak bonding between the filler and matrix may induce problems. 

There are two types of bone (a) compact or cortical bone and (b) trabecular or cancellous bone. Cortical bone is found principally in the shafts (diaphyses) of long bones. It consists of a number of irregularly spaced overlapping cylindrical units termed Haversian systems. Each consists of a central Haversian canal surrounded by concentric lamellae of bony tissue. Trabecular bone is found principally at the ends of long bones and flat bones. It is composed of a meshwork of trabeculae within which... 

The skeleton consists of approximately 80 % cortical bone and 20 % trabecular bone, mainly in the axial skeleton. These amounts vary according to site and relate to the need for mechanical support. While trabecular bone accounts for the minority of total skeletal tissue, it is the site of greater bone turnover because its total surface area is greater than that of cortical bone. 

Tab. 12.3 Fracture toughness (K c) values of a conventional sol-gel glass, star gels and those obtained for human cortical bone by different authors.

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