Osteon
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| Diagram of compact bone from a transverse section of a long bone's cortex. | |
| Gray's | subject #18 89 |
The osteon or Haversian system is the fundamental functional unit of compact bone. Osteons are roughly cylindrical structures that are typically several millimeters long and around 0.2mm in diameter.[1] They are present in many bones of most mammals and some bird species.
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[edit] Description
Each osteon consists of concentric layers, or lamellae, of compact bone tissue that surround a central canal, the Haversian canal. The Haversian canal contains the bone's nerve and blood supplies. The boundary of an osteon is the cement line.
Between adjoining osteons there are angular intervals that are occupied by interstitial lamellae. These lamellae are remnants of osteons the greater parts of which have been destroyed. Near the surface of the compact bone the lamellae are arranged parallel to the surface; these are called circumferential lamellae. Some of the osteoblasts develop into osteocytes, each living within its own small space, or lacuna. Osteocytes make contact with the cytoplasmic processes of their counterparts via a network of small transverse canals, or canaliculi. This network facilitates the exchange of nutrients and metabolic waste.
Collagen fibers in a particular lamella run parallel to each other but the orientation of collagen fibers within other lamellae is oblique. The collagen fiber density is lowest at the seams between lamellae, accounting for the distinctive microscopic appearance of a transverse section of osteons.
The space between osteons is occupied by interstitial lamellae, which are the remnants of osteons that were partially resorbed during the process of bone remodelling.
Osteons are connected to each other and the periosteum by oblique channels called Volkmann's canals.
[edit] Bioarchaeology and forensic investigation
Osteons can be used to determine the sex of an individual[2] and age, as well as aspects of health and motor history[3] and diet. Osteons and their arrangement also vary according to taxon, so that genus and sometimes species can be differentiated using a bone fragment not otherwise identifiable, though there is considerable variability among the different bones of a skeleton, and features of some faunal osteons overlap with those of human osteons; therefore, examination of osteons is not of primary use in the analyses of osteological remains.[4] More research is needed, but has the potential to positively affect the studies in bioarchaeology, paleontology and forensic investigations.
[edit] Drifting Osteons
Drifting osteons are a phenomenon that is not fully understood. A "drifting osteon" is classified as one that runs both longitudinally as well as transversely through the cortex. An osteon can "drift" in one direction or change directions several times, leaving a tail of lamellae behind the advancing haversian canal.[5]
[edit] See also
- Haversian canals
- Cortical bone (compact bone)
- Cancellous bone (spongy bone containing no osteons)
[edit] References
- ^ "Osteon," Encyclopædia Britannica Online (2009); retrieved 23 June 2009.
- ^ Monika Martiniaková,Radoslav Omelka,Birgit Grosskopf, Alexander V. Sirotkin,and Peter Chrenek, 2008, "Sex-related variation in compact bone microstructure of the femoral diaphysis in juvenile rabbits," Acta Vet Scand. 50(1): 15ff
- ^ Pfeiffer, Susan; Crowder, Christian; Harrington, Lesley; and Brown, Michael, 2006, "Secondary Osteon and Haversian Canal Dimensions as Behavioral Indicators," American Journal of Physical Anthropology, 131 (4): 460 - 468
- ^ Martiniaková, Monika. 2006. Differences in Bone Microstructure of Mammalian Skeletons. Faculty of Natural Sciences, Constantine the Philosopher University in Nitra: Nitra, Slovakia
- ^ Robling, Alexander D.; Stout, Sam D. 1999 "Morphology or the Drifting Osteon," Cells Tissues Organs 164:192-204
[edit] Bibliography
- Cooper, Reginald R.; Milgram, James W.; and Robinson, Robert A. 1966 "Morphology of the Osteon: An Electron Microscopic Study," Journal of Bone and Joint Surgery, 48:1239-1271.
- Martiniaková, Monika 2006 Differences in Bone Microstructure of Mammalian Skeletons. Faculty of Natural Sciences, Constantine the Philosopher University in Nitra: Nitra, Slovakia.
- Netter, Frank H. (1987), Musculoskeletal system: anatomy, physiology, and metabolic disorders. Summit, New Jersey: Ciba-Geigy Corporation ISBN 0-914168-88-6
- Pfeiffer, Susan; Crowder, Christian; Harrington, Lesley; and Brown, Michael 2006 "Secondary Osteon and Haversian Canal Dimensions as Behavioral Indicators," American Journal of Physical Anthropology, 131 (4): 460 - 468.
- Robling, Alexander D.; Stout, Sam D. 1999 "Morphology or the Drifting Osteon," Cells Tissues Organs 164:192-204
[edit] External links
- SLIBS Bone Website: http://www.trinity.edu/rblyston/bone/intro2.htm
- MeSH Haversian+System
- Bioweb at UWLAX Bone model
- Histology of osteons
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