Haversian canal

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Haversian canals^[i] (sometimescanals of Havers,osteonic canals orcentral canals) are a series of microscopic tubes in the outermost region of bone calledcortical bone. They allow blood vessels and nerves to travel through them to supply theosteocytes.

Haversian canal
Diagram of compact bone from a transverse section of a typical long bone's cortex.
Identifiers
FMA	224787
Anatomical terminology [edit on Wikidata]

Diagram of a typical long bone showing both cortical (compact) and cancellous (spongy) bone.

Structure

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Each Haversian canal generally contains one or twocapillaries and manynerve fibres. The channels are formed by concentric layers calledlamellae, which are approximately 50 μm indiameter. The Haversian canals surroundblood vessels andnerve cells throughout bones andcommunicate withosteocytes (contained in spaces within the dense bone matrix calledlacunae) through connections calledcanaliculi. This unique arrangement is conducive to mineral salt deposits and storage which givesbone tissue its strength.Active transport is used to move most substances between the blood vessels and the osteocytes.^[1]

Haversian canals are contained withinosteons, which are typically arranged along the long axis of the bone in parallel to the surface. The canals and the surrounding lamellae (8-15) form the functional unit, called a Haversian system, orosteon.

Clinical significance

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Fracture

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Blood vessels in the Haversian canals are likely to be damaged bybone fracture.^[2] This can causehaematoma.^[2]

Rheumatoid arthritis

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Haversian canals may be wider in patients withrheumatoid arthritis.^[3] They are also more likely to containosteoclasts that break down bone structure.^[3] These differences are studied withlight microscopy.^[3]

History

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Haversian canals were first described (and probably discovered) byBritish physician Clopton Havers, after whom they are named.^[4] He described them in his 1691 workOsteologica Nova.^[5]

In different animals

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Human bones are densely vascularized as in many other mammals. Even though some authors tried to identify a correlation betweenendothermy and secondary Haversian reconstruction, this feature is absent in many living mammals (e.g.monotremes,Talpa,flying foxes,Herpestes,Dasypus) and birds (Aratinga,Morococcyx,Nyctidromus,Momotus,Chloroceryle) while others possess only scattered Haversian systems (e.g.artiodactyls,Didelphis,Anas,Gallus,turkey,helmeted guineafowl). Scattered Haversian canals are also found in ectotherms likecryptodire turtles.^[6] Among extinct groups, dense Haversian vascularization is only present in stem-birds (dinosaurs) and stem-mammals (therapsids)^[7] while scattered Haversian systems can be found inichthyosaurs,phytosaurs, basal stem-mammals (e.g.Ophiacodon),Limnoscelis, andtemnospondyls. Whenendosteal Haversian systems are considered, the phylogenetic distribution becomes even broader.^[6]

Notes

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^As with othermedical eponyms, the adjective derived from the eponym's name is usually lowercased; thushaversian (butcanal of Havers),fallopian,eustachian, andparkinsonism (butParkinson disease); for more, seeeponym > orthographic conventions.

References

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^Dahl, A. C. E.; Thompson, M. S. (2011-01-01), Moo-Young, Murray (ed.),"5.18 - Mechanobiology of Bone",Comprehensive Biotechnology (Second Edition), Burlington: Academic Press, pp. 217–236,ISBN 978-0-08-088504-9, retrieved2021-01-15
^^a ^bWhite, Tim D.; Folkens, Pieter A. (2005-01-01), White, Tim D.; Folkens, Pieter A. (eds.),"Chapter 4 - BONE BIOLOGY & VARIATION",The Human Bone Manual, San Diego: Academic Press, pp. 31–48,ISBN 978-0-12-088467-4, retrieved2021-01-15
^^a ^b ^cAeberli, D. (2014-01-01),"Skeleton, Inflammatory Diseases of",Reference Module in Biomedical Sciences, Elsevier,ISBN 978-0-12-801238-3, retrieved2021-01-15
^Sparks, David S.; Saleh, Daniel B.; Rozen, Warren M.; Hutmacher, Dietmar W.; Schuetz, Michael A.; Wagels, Michael (2017-01-01)."Vascularised bone transfer: History, blood supply and contemporary problems".Journal of Plastic, Reconstructive & Aesthetic Surgery.70 (1):1–11.doi:10.1016/j.bjps.2016.07.012.ISSN 1748-6815.PMID 27843061.
^Havers, Clopton (1729).Osteologia Nova: Or, Some New Observations of the Bones, and the Parts Belonging to Them; with the Manner of Their Accretion and Nutrition: Communicated to the Royal Society in Several Discourses ... To which is Added, a Fifth Discourse, of the Cartilages. The Second Edition. By Clopton Havers . W. Innys.
^^a ^bBouvier, Marianne (1977)."DINOSAUR HAVERSIAN BONE AND ENDOTHERMY".Evolution.31 (2):449–450.doi:10.1111/j.1558-5646.1977.tb01028.x.
^Enlow, Donald H. (1969). "The bones of reptiles".Biology of the Reptilia. Vol. 1. Academic Press. pp. 45–81.

External links

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http://www.lab.anhb.uwa.edu.au/mb140/Archived 2010-12-01 at theWayback Machine
"Bone Anatomy - Haversian canals within bone". November 4, 2006.Archived from the original on 2021-12-13 – viaYouTube. Video of haversian canal system within cortical bone.

Additional images

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Bone by decalcification (40x):
1. Volkmann's canal
2. Haversian canal
3. Blood vessel
Bone by decalcification (100x):
1. Volkmann's canal
2. Haversian canal
3. Lacuna
4. Lamella