has part has part occurs in characteristic of has modifier ossification Abnormal bone structure Abnormal bone ossification All bones are formed by the replacement by osteocytes of mesenchyme-derived connective tissue. Intramembranous ossification refers to the direct replacement of primitive mesenchyme with bone, and is responsible for bones such as the calvarium (e.g., frontals, parietals, interparietal) and the clavicula. In endochondral ossification, the mesenchyme differentiates into a cartilaginous intermediate, which serves as a template (anlange) that is subsequently removed and replaced by bone. Most bones are formed via endochondral ossification, including those at the base of the skull, the vertebral column, pectoral and pelvic regions and long bones of the extremities. A reduction in the amount of mineralized bone compared with that expected for a given developmental age. In clinicakl parlance, reduced ossification and delayed ossification are often used synonymously, but in principle a bone delayed ossification in a child can display normal ossification at a later developmental stage. The HPO will therefore treat poor, reduced, and decreased officiation as synonymous, and delayed ossification as a specific kind of reduced ossification. quality abnormal bone element