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Osteons on cross-section of a bone. 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]
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).
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. Bones come in a variety of shapes and sizes and have complex internal and external ...
It is composed of 270 bones at the time of birth, [2] but later decreases to 206: 80 bones in the axial skeleton and 126 bones in the appendicular skeleton. 172 of 206 bones are part of a pair and the remaining 34 are unpaired. [3] Many small accessory bones, such as sesamoid bones, are not included in this.
In an ordinary microscopic section, viewed by transmitted light, they appear as fusiform opaque spots. Each lacuna is occupied during life by a branched cell, termed an osteocyte, bone-cell or bone-corpuscle. Lacunae are connected to one another by small canals called canaliculi. A lacuna never contains more than one osteocyte.
They are the most common cell type in bone (31,900 per cubic millimeter in bovine bone to 93,200 per cubic millimeter in rat bone). [6] Most of the receptor activities that play an important role in bone function are present in the mature osteocyte. [6] Osteocytes are an important regulator of bone mass.
Bone tissue is a dynamic system with active metabolism. [24] Bone tissue remodelling or bone remodeling is a successive chain of old bone matrix removal and its replacement with a new one. [25] These processes make a child’s skeleton grow and extend, while childhood is characterized by bone tissue growth rather than its resorption.
Major features of the bone-forming complex, the osteon, composed of osteoblasts and osteocytes. At least one more regulated transport process is involved. The stoichiometry of bone mineral basically is that of hydroxyapatite precipitating from phosphate, calcium, and water at a slightly alkaline pH : [ 29 ]