Sometimes according to where the formation of bone tissue is classified as “periosteal” or “endosteal”.
The basis for either bone formation or bone resorption is the same, regardless of the type of membrane involved. Intramembranous bone formation is found in the growth of the skull and is also found in the sphenoid and mandible even though it consists of endochondral elements, where the endochondral and intramembranous growth process occurs in the same bone. In the eighth week, reinforcement center appears in the calvarial and facial areas in areas where there is a mild stress strength. The earliest evidence of intramembranous bone formation of the skull occurs in the mandible during the sixth prenatal week. In the craniofacial cartilage bones, intramembranous ossification originates from nerve crest cells. If bone growth continues, the lamella will be embedded behind the new bone surface and be replaced by the haversian canal system.ĭuring intramembranous bone formation, the connective tissue membrane of undifferentiated mesenchymal cells changes into bone and matrix bone cells. Increased thickness or width of the bone is caused by deposition of new bone in the form of circumferential lamellae under the periosteum. The direction of bone formation in the epiphysis plane is determined by the direction and distribution of the pressure line. The growth rate is not always the same in all parts, for example, faster in the proximal end than the distal humerus because the internal pattern of the spongiosum depends on the direction of bone pressure. The same formative cells form two types of bone formation and the final structure is not much different.īone growth depends on genetic and environmental factors, including hormonal effects, diet and mechanical factors. Second is the endochondral ossification in which bone tissue replaces a preexisting hyaline cartilage, for example during skull base formation. The bone seen from its development can be divided into two processes: first is the intramembranous ossification in which bones form directly in the form of primitive mesenchymal connective tissue, such as the mandible, maxilla and skull bones. Bone-forming cells, osteoblasts, osteoclast play an important role in determining bone growth, thickness of the cortical layer and structural arrangement of the lamellae.īone continues to change its internal structure to reach the functional needs and these changes occur through the activity of osteoclasts and osteoblasts.
Bone has vascular tissue and cellular activity products, especially during growth which is very dependent on the blood supply as basic source and hormones that greatly regulate this growth process. The solid part remainder consisting of various minerals, especially 76% of calcium salt and 33% of cellular material. Then the subsequent stages of endochondral ossification will take place in several zones of the bone.īone is living tissue that is the hardest among other connective tissues in the body, consists of 50% water. After the primary ossification center is formed, the marrow cavity begins to expand toward the epiphysis. After this formation, chondrocytes in the central region of the cartilage start to proceed with maturation into hypertrophic chondrocytes. Endochondral ossification will form the center of primary ossification, and the cartilage extends by proliferation of chondrocytes and deposition of cartilage matrix. After that, the bone will be reshaped and replaced by mature lamellar bone. This cell will synthesize bone matrix in the periphery and the mesenchymal cells continue to differentiate into osteoblasts. In this process, mesenchymal cells proliferate into areas that have high vascularization in embryonic connective tissue in the formation of cell condensation or primary ossification centers. In intramembranous ossification, bone development occurs directly. Based on its embryological origin, there are two types of ossification, called intramembranous ossification that occurs in mesenchymal cells that differentiate into osteoblast in the ossification center directly without prior cartilage formation and endochondral ossification in which bone tissue mineralization is formed through cartilage formation first. After progenitor cells form osteoblastic lines, they proceed with three stages of development of cell differentiation, called proliferation, maturation of matrix, and mineralization.
The process of bone formation is called osteogenesis or ossification.
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