Cartilage Is Capable of Two Kinds of Growth, Appositional and Interstitial

With the onset of matrix secretion, cartilage growth will continue by a combination of two processes:

• Appositional growth, the process that forms new car­tilage at the surface of preexisting cartilage

• Interstitial growth, the process that forms new cartilage within the cartilage mass

The new cartilage cells produced in the process of ap­positional growth derive from the inner portion of the sur­rounding perichondrium.

The new cartilage cells produced in the process of interstitial growth arise from division of chondrocytes within their lacunae.

Hyaline cartilage when calcified is generally replaced by bone.

BONE FORMATION

The Development of a Bone Is Traditionally Classified as Endochondral or Intramembranous

The distinction between endochondral and intramem­branous formation rests on whether a cartilage model serves as the precursor of the bone (endochondral ossification) or whether the bone is formed by a simpler method, without the intervention of a cartilage precursor (intramembranous ossification). The bones of the extremities and those parts of the axial skeleton that bear weight (e.g., vertebrae) de­velop by endochondral ossification. The flat bones of the skull and face, the mandible, and the clavicle develop by intramembranous ossification.

Дата добавления: 2015-07-25