Osteon
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| Osteon | |
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| A light micrograph of a transverse section of human compact bone. X 250 | |
| Gray's | subject #18 89 |
| Dorlands/Elsevier | o_08/12601039 |
The osteon, or Haversian system, is the fundamental functional unit of compact bone. Osteons are present in many of the bones of most mammals, birds, reptiles, and amphibians.
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. Osteoblasts form the lamellae sequentially, from the most external inward toward the Haversian canal. 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 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.
Osteons are separated from each other by cement lines. Collagen fibers and canaliculi do not cross cement lines.
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.
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[edit] Use in archaeology and forensics
Osteons carry their history so that given the right conditions they can be used to "read" the sex, age, health history, motor history and diet of an individual whose bone is being studied. 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. This is of use in archaeology, paleontology and forensics.
[edit] See also
[edit] References
- 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 0914168886
- Pfeiffer, Susan; Crowder, Christian; Harrington, Lesley; and Brown, Brown 2006 "Secondary Osteon and Haversian Canal Dimensions as Behavioral Indicators," American Journal of Physical Anthropology, 131 (4): 460 - 468.
[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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