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==Introduction==

==Introduction==

Osteogenesis is the formation of bone. Bone forms from one of three lineages; the skull forms from neural cest; the limb skeleton forms from lateral plate mesoderm; and the axial skeleton forms from paraxial mesoderm (sclerotome). There are two methods of osteogenesis. Both involve the transformation of pre - existing mesenchymal tissue into bone.

Osteogenesis is the formation of [[Bones and Cartilage - Anatomy & Physiology#Types of Bone|bone]]. Bone forms from one of three lineages; the skull forms from [[Developmental Biology - Neurogenesis - Anatomy & Physiology#Neural Crest|neural cest]]; the limb skeleton forms from lateral plate mesoderm; and the axial skeleton forms from paraxial mesoderm (sclerotome). There are two methods of osteogenesis. Both involve the transformation of pre - existing mesenchymal tissue into bone.

#'''Intramembranous Ossification''' - direct conversion of mesenchymal tissue into bone. Occurs in production of the skull.

#'''Intramembranous Ossification''' - direct conversion of mesenchymal tissue into bone. Occurs in production of the skull.

#'''Endochondrial Ossification''' - mesechymal tissue first differentiates into cartilage, then into bone. This occurs in the production of limb and axial skeleton.

#'''Endochondrial Ossification''' - mesechymal tissue first differentiates into [[Bones and Cartilage - Anatomy & Physiology#Structure and Function of Cartilage|cartilage]], then into bone. This occurs in the production of limb and axial skeleton.

#*Limb cartilage is produced in a proximal to distal direction as a continuous structure. It becomes punctuated with joints later, and then converted to bone.

#*Limb cartilage is produced in a proximal to distal direction as a continuous structure. It becomes punctuated with [[Developmental Biology - Anatomy & Physiology#Joints|joints]] later, and then converted to bone.