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Haversian canals [i] (sometimes canals of Havers, osteonic canals or central canals) are a series of microscopic tubes in the outermost region of bone called cortical bone. They allow blood vessels and nerves to travel through them to supply the osteocytes .
In osteology, the osteon or haversian system (/ h ə ˈ v ɜːr. ʒ ən /; named for Clopton Havers) is the fundamental functional unit of much compact bone. Osteons are roughly cylindrical structures that are typically between 0.25 mm and 0.35 mm in diameter . [ 1 ]
A bone is a rigid organ [1] that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, and enable mobility.
Diameter of canaliculi in human bone is approximately 200 to 900 nm. [1] In bovine tibia diameter of canaliculi was found to vary from 155 to 844 nm (average 426 nm). [ 2 ] In mice humeri it varies from 80 to 710 nm (average 259 nm), while diameter of osteocytic processes varies from 50 to 410 nm (average 104 nm).
The cartilage cells or chondrocytes are contained in cavities in the matrix, called cartilage lacunae; around these, the matrix is arranged in concentric lines as if it had been formed in successive portions around the cartilage cells. This constitutes the so-called capsule of the space.
Hyaline cartilage has fewer cells than elastic cartilage; there is more intercellular space. Hyaline cartilage is found in the nose, ears, trachea, parts of the larynx, and smaller respiratory tubes. Fibrous cartilage has the fewest cells so it has the most intercellular space. Fibrous cartilage is found in the spine and the menisci.
Flat bones are bones whose principal function is either extensive protection or the provision of broad surfaces for muscular attachment. These bones are expanded into broad, flat plates , [ 1 ] as in the cranium ( skull ), the ilium, ischium, and pubis ( pelvis ), sternum and the rib cage .
Stromal cell-derived factor 1 (SDF-1) and CXCR4 mediate recruitment of mesenchymal stem cells. IL-1 and IL-6 are the most important cytokines for bone healing. IL-1 promotes formation of callus and of blood vessels. IL-6 promotes differentiation of osteoblasts and osteoclasts. [4] All cells within the blood clot degenerate and die.