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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 ]
Endochondral ossification is responsible for development of most bones including long and short bones, [4] the bones of the axial (ribs and vertebrae) and the appendicular skeleton (e.g. upper and lower limbs), [5] the bones of the skull base (including the ethmoid and sphenoid bones) [6] and the medial end of the clavicle. [7]
They are located on the surface of osteon seams and make a protein mixture known as osteoid, which mineralizes to become bone. [23] The osteoid seam is a narrow region of a newly formed organic matrix, not yet mineralized, located on the surface of a bone. Osteoid is primarily composed of Type I collagen.
Bone is broken down by osteoclasts, and rebuilt by osteoblasts, both of which communicate through cytokine (TGF-β, IGF) signalling.Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts.
Materials picked up by osteocytes adjacent to blood vessels are distributed throughout the bone matrix via the canaliculi. 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 ]
The periosteum is a membrane that covers the outer surface of all bones, [1] except at the articular surfaces (i.e. the parts within a joint space) of long bones. (At the joints of long bones the bone's outer surface is lined with "articular cartilage", a type of hyaline cartilage.)
This is a KFF Health News story. Preparing cancer patients for difficult decisions is an oncologist's job. At the University of Pennsylvania Health System, doctors are nudged to talk about a ...
They grow primarily by elongation of the diaphysis, with an epiphysis at each end of the growing bone. The ends of epiphyses are covered with hyaline cartilage ("articular cartilage"). The longitudinal growth of long bones is a result of endochondral ossification at the epiphyseal plate.