Appositional Growth

Appositional Growth (from Latin apponere - to add, to apply), growth resulting from the superposition of new layers. Appositional growth is defined as the increase in size of any structural formation, tissue, or organ, which occurs not through the introduction of new particles between previously existing ones (see Intussusception) and not through the multiplication of tissue cells or the increase in mass of intercellular substance (interstitial growth), but through the superposition of new layers from the surface onto already formed areas. An example of appositional growth can be the growth of concretions, the thickening in some cases of cell walls, the formation of new layers of wood in a tree, and the growth of cartilage and developing bone. The growth of embryonic cartilage occurs not only through the multiplication of cells and the increase of the ground substance between them, but also by the addition to already formed areas on the surface of new layers of mesenchyme that transforms into cartilage tissue. The process of the deposition of bone plates from the side of the periosteum (periosteal ossification) is called appositional growth of bone.