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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]
The process of endochondral ossification, which converts the cartilage models into bone, begins by the twelfth week of embryonic development. At birth, ossification of much of the bone has occurred, but the hyaline cartilage of the epiphyseal plate will remain throughout childhood and adolescence to allow for bone lengthening.
A spotted gar larva at 22 days stained for cartilage (blue) and bone (red). Chondrogenesis is the biological process through which cartilage tissue is formed and developed. . This intricate and tightly regulated cellular differentiation pathway plays a crucial role in skeletal development, as cartilage serves as a fundamental component of the embryonic skele
Diagram showing stages of endochondral ossification. Endochondral ossification is the formation of long bones and other bones. This requires a hyaline cartilage precursor. There are two centers of ossification for endochondral ossification. The primary center. In long bones, bone tissue first appears in the diaphysis (middle of shaft).
The longitudinal growth of long bones is a result of endochondral ossification at the epiphyseal plate. Bone growth in length is stimulated by the production of growth hormone (GH), a secretion of the anterior lobe of the pituitary gland .
An ossification center is a point where ossification of the hyaline cartilage begins. The first step in ossification is that the chondrocytes at this point become hypertrophic and arrange themselves in rows. [1] The matrix in which they are imbedded increases in quantity, so that the cells become further separated from each other.
TGF-β determines and regulates cell lineages during endochondral ossification through Sox9 and Runx2 signalling pathways. TGF-β will act as a stimulator of chondrogenesis, and an inhibitor of osteoblastic differentiation, by blocking the Runx2 factor through Smad3 activation. Sox9 stimulates differentiation into chondrocytes.
The Haversian system forms during the process of endochondral ossification, which starts with a cartilage template that is gradually replaced by bone tissue. Osteoblasts , the bone-forming cells, secrete the organic components of bone matrix [osteoid] and then initiates its mineralization.