The beginning organic matrix of bone. Initial deposit in bone formation starts with the deposition of osteoid, which is secreted by mature osteoblasts at a speed of 1–2 μm per day. When concerned with lamellar bone, a matrix composed of a scaffold of interwoven collagen fibers (mainly type 1) and noncollagenous proteins is sedimented as osteocalcin and bone sialoprotein – unique for the mineralized tissues – as well as osteonectin, osteopontin, and a number of growth factors. The mean thickness of osteoid in lamellar bone formation is 10 μm; when this thickness is reached, mineralization as sedimentation of crystals of carbonated hydroxyapatite (Ca10(PO4)6(OH2)) takes place.
Similar in appearance to bone. It can also refer to the early matrix or layer of real bone where calcium salts are deposited to create fully developed bone tissue.