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Once activated, osteoclasts move to areas of microfracture in the bone by chemotaxis. Osteoclasts lie in small cavities called Howship's lacunae, formed from the digestion of the underlying bone. The sealing zone is the attachment of the osteoclast's plasma membrane to the underlying bone.
The human body is in a constant state of bone remodeling. [4] Bone remodeling is a process which maintains bone strength and ion homeostasis by replacing discrete parts of old bone with newly synthesized packets of proteinaceous matrix. [5] Bone is resorbed by osteoclasts, and is deposited by osteoblasts in a process called ossification. [6]
Osteoclasts are multinucleated cells that derive from hematopoietic progenitors in the bone marrow which also give rise to monocytes in peripheral blood. [6] Osteoclasts break down bone tissue, and along with osteoblasts and osteocytes form the structural components of bone. In the hollow within bones are many other cell types of the bone marrow.
Bone is broken down by osteoclasts, and rebuilt by osteoblasts, both of which communicate through cytokine (TGF-β, IGF) signalling. Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. [1]
Bone tissue is removed by osteoclasts, and then new bone tissue is formed by osteoblasts. Both processes utilize cytokine (TGF-β, IGF) signalling.In osteology, bone remodeling or bone metabolism is a lifelong process where mature bone tissue is removed from the skeleton (a process called bone resorption) and new bone tissue is formed (a process called ossification or new bone formation).
New bone is then formed by the osteoblasts. Bone is constantly remodeled by the resorption of osteoclasts and created by osteoblasts. [21] Osteoclasts are large cells with multiple nuclei located on bone surfaces in what are called Howship's lacunae (or resorption pits).
Many believed osteoclasts and osteoblasts came from the same progenitor cell. Because of this, osteoclasts were thought to be derived from cells in connective tissue. Studies that observed that bone resorption could be restored by bone marrow and spleen transplants helped prove osteoclasts' hematopoietic origin. [3]
Instead of becoming cartilage cells (chondrocytes), they mature into bone-building osteoblasts. [5] This newly formed bone can be called "periosteal bone" as it originates from the transformed periosteum. However, considering its developmental pathway, it could be classified as "intramembranous bone". [8]