<unk>  is one of the two essential processes during fetal development of the gnathostome (excluding chondrichthyans such as sharks) skeletal system by which rudimentary bone tissue is created.<unk>  is also an essential process during the natural healing of bone fractures and the rudimentary formation of bones of the head. Transmission electron micrograph of a mesenchymal stem cell that is displaying typical ultrastructural characteristics. Unlike endochondral<unk> , which is the other process by which bone tissue is created during fetal development, cartilage is not present during<unk> .
Intramembranous ossification
Heterotopic ossification
Fibrochondrogenesis
Endochondral ossification
Hypercementosis
Craterization
Fibrocartilage callus
Metastatic calcification