Axial skeleton

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. 

Ke HZ, Chen HK, Qi H, Pirie CM, Simmons HA, Ma YF, et al. (1995a) Effects of droloxifene on prevention of cancellous bone loss and bone turnover in the axial skeleton of aged, ovariectomized rats. Bone 17 491-496... 

C. Schiepers, J. Nuyts, G. Bormans, J. Dequeker, R. Bouillon, L. Mortelmans, A. Verbruggen, R.M. De, Fluoride kinetics of the axial skeleton measured in vivo with fluorine-18-fluoride PET, J. Nucl. Med. 38(12) (1997) 1970-1976. 

During evaluation, skeletal elements like lower jaw, sternum, and limbs may cautiously be parted from the skull or axial skeleton. The following is an example of the procedure which may be followed ... 

Remove right forelimb (clavicle remains with axial skeleton), and examine scapula including tuberositas delteoidea, humerus, radius, ulna, metacarpals, and phalanges from all aspects. 

Fig. 1. Imaging of the developmental progress of the mouse axial skeleton by micro-CT can be achieved by serial endpoint harvest, (a) Partial ossification is observed in embryonic day 15 (El 5) specimen skeleton, (b) Rapid growth and ossification can be appreciated between E15 and Et 8 mouse specimens, (c) Postnatal specimens (PO) are also amenable to micro-CT scanning, (d) Eurther developmental stages from juvenile to adult (shown) can be imaged as well.

After multiday exposures, there was an increased frequency of malformations of the axial skeleton involving the head, sternum, ribs, and vertebrae. About 90% of the fetuses exposed on gestation day 9 had only 6 cervical vertebrae 60% of the fetuses exposed on gestation day 10 had reduced survival and a reduction in the number of thoracic and lumbar... 

Hematopoietic development of blood cells begins mainly in the spleen and liver of the fetus during early pregnancy. By the seventh month, however, the marrow of a fetus becomes the primary site of blood cell formation [1]. During childhood, the marrow of the central axial skeleton such as the pelvis, spinal cord, and ribs, and of the extremities, such as the wrist and ankle, provides the key site of hematopoiesis. Hematopoiesis at the periphery (also known as extramedullary hematopoiesis) slowly decreases with age. Chronic administration of hematopoietic growth factors can reverse this decline. Severe hemolytic anemia and hematopoietic malignancies can also reverse the process. 

Production of blood cells in bone marrow of the central axial skeleton is referred to as medullary hematopoiesis. Hematopoietic tissue in adult bone marrow is well perfused and contains fat cells (adipocytes), and various types of blood and blood precursor cells encased within a protein matrix. Fibroblast, stromal and endothelial cells within bone marrow, serve as sources of matrix proteins as well as a factory for growth factors and chemokines that regulate blood cell production and release matured cells into the circulation [2,3]. Chemokines act as signal lamps for trafficking of lymphocytes in and out of lymphoid tissues. Erythroblasts, neutrophils, lymphoblasts, macrophages, megakaryocytes, and pluripotent stem cells are also found within the calcihed lattice crisscrossing the marrow space. 

Diethanolamine was painted as an aqueous solution on the skin of CD rats on days 6-15 of gestation at dose levels of 0, 150, 500 and 1500 mg/kg bw per day. The two higher dose levels produced severe skin irritation. There was no effect of any treatments on fetal weight or on the incidence of external, visceral or skeletal abnormalities, but delayed ossification of the axial skeleton and distal appendages was observed in fetuses of the 1500-mg/kg bw group (Marty et al, 1999). 

Because elements that will later form the CNS appear earlier than most other systems in the developmental process, disturbances of neurulation may result in severe abnormalities of the brain and spinal cord. Other ectodermal thickenings, the otic placode and lens placode, develop into the inner ear and lens, respectively. A series of mesodermal blocks called somites form around the neural tube, and these somites give rise to the axial skeleton. The intraembryonic coelom appears in the lateral mesoderm and later divides into the pericardial, pleural and peritoneal cavities. The intermediate mesoderm forms the nephrogenic cord, which later becomes the kidneys. 

Tallquist, M. D., Weismann, K. E., Hell-strom, M. and Soriano, P. (2000) Early myotome specification regulates PDGFA expression and axial skeleton development. Development 127, 5059-5070. 

Certaiu medicatious have beeu associated with au iucrease iu osteoporosis risk, particularly steroids and anticonvulsants. Steroid-induced osteoporosis arises due to use of glucocorticoids, analogous to Cushing s syndrome, and involving mainly the axial skeleton prednisone... 

Adequate calcium nutrition during childhood and adolescence is thought to bean important deterrent to osteoporosis in later life. A one-year study of 149 girls (8 years old) revealed the effects of consuming a typical diet (900 mg Ca/day) or a diet supplemented with an additional 850 mg Ca/day Bonjour el al, 1997). The Ca supplement was supplied by specially prepared biscuits, juices, and candy bars (rather thar pills) to assure compliance. To view some of the data, the density at the femoral diaphysis increased by 5% (unsupplemented) and by 6% (plus calcium) during the 1-ycar period. The density at the lumbar spine increased by 4% (unsupplemented) and by 4% (plus calcium). The data dernonstrated a dear and definite increase in bone density at some sites, but not at others. This study, as well as others Johnston et al., 1992), tend to show that caicium supplements to children can benefit bones of the appendicular skeleton, but not the axial skeleton. The appendicular skeleton includes the pelvis, arm bones, and leg bones. The axial skeleton includes the skull, vertebra, ribs, and sternum. 

Figure 2 External appearance of various types of human craniorachischisis totalis (total myeloschisis) illustrating the severity of the dysraphic disorders. The first fetus (a) illustrates the severity of the lordosis and the shortness of the axial skeleton which can occur in these disorders. The exposed areas of the central nervous system are totally destroyed. In (b), note the exencephalic brain (termed area cerebrovasculosa). (c, d) Lateral and posterior view. Compare (c) with Figure 1. In (d), the destroyed areas of brain and spinal cord tissues have been removed to show the severity of the malformations of the vertebrae. (Reproduced from Marin-Padilla M (1978) Clinical and experimental rachischisis. In Congenital Malformations of the Spine and Spinal Cord. vol. 32. Handbook of Clinical Neurology. Amsterdam North-Holland, with permission from Elsevier.)...

Chordoma is a malignant tumor with notochord-like differentiation that principally occurs in apposition to the axial skeleton peripheral lesions are extremely 505,506 Differential diagnosis includes metastatic... 

Kieny, M., Mauger, A., Sengel, P. 1972. Early regionalization of somitic mesoderm as studied by the development of axial skeleton of the chick embryo. Dev. Biol. 28, 142-161. 

In rats and dogs following absorption of plutonium from the gastrointestinal tract, up to 95X of the absorbed dose has been found to be distributed to the skeleton (Carritt et al. 1947 Larsen et al. 1981 Toohey et al. 1984). Plutonium was also distributed to a less extent to the liver, carcass, and soft tissues (Carritt et al. 1947 Katz et al. 1955 Larsen et al. 1981 Sullivan et al. 1984). The distribution of plutonium-237 in a bicarbonate solution administered via a gelatin capsule was greatest to the axial skeleton (Toohey et al. 1984). 

Swiderski, R.E. Solursh, M. (1992a). Localization of type II collagen, long form al(IX) collagen, and short form al(IX) collagen transcripts in the developing chick notochord and axial skeleton. Dev. Dynamics, 194, 118-27. 

Celecoxib (CEL), 4-[5-(4-methylphenyl)-3-(trifluoromethyl)-lH-pyrazol-l-yl]benzenesulfonamide, used for the relief from symptoms of ankylosing spondylitis, a chronic inflammatory disease of the axial skeleton, has been determined elecSrochemically by a PANI grafted NH2-MWCNT electrode [53]. Aniline was electrochemically polymerized in presence of NH2-MWCNTS on an indium tin oxide (ITO) electrode. The composite film had a lai e surface area and showed a stripping DPV signal from CEL reduction after an accumulation time of only 30 s at -0.5 V. With stripping SWV, ten times higher peak currents were detected. 

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