Bone ossification, or osteogenesis, is the process of bone formation. This process begins between the sixth and seventh weeks of embryonic development and continues until about age twenty-five; although this varies slightly based on the individual. There are two types of bone ossification, intramembranous and endochondral. Each of these processes begins with a mesenchymal tissue precursor, but how it transforms into bone differs. Intramembranous ossification directly converts the mesenchymal tissue to bone and forms the flat bones of the skull, clavicle, and most of the cranial bones. Endochondral ossification begins with mesenchymal tissue transforming into a cartilage intermediate, which is later replaced by bone and forms the remainder of the axial skeleton and the long bones.
The development of the skeleton can be traced back to three derivatives[1]: cranial neural crest cells, somites, and the lateral plate mesoderm. Cranial neural crest cells form the flat bones of the skull, clavicle, and the cranial bones (excluding a portion of the temporal and occipital bones. Somites form the remainder of the axial skeleton. The lateral plate mesoderm forms the long bones
Review Sheet Exercise 8 The Axial Skeleton Pdf Download
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