osteoclast

Examples of osteoclast in the following topics:

• Cell Types in Bones

  • The osteoblast, osteoclast, osteocyte, and osteoprogenitor bone cells are responsible for the growing, shaping, and maintenance of bones.
  • Bone consists of four types of cells: osteoblasts, osteoclasts, osteocytes, and osteoprogenitor (or osteogenic) cells .
  • Osteoclasts continually break down old bone while osteoblasts continually form new bone.
  • The ongoing balance between osteoblasts and osteoclasts is responsible for the constant, but subtle, reshaping of bone.
  • Osteoclasts develop from monocytes and macrophages and differ in appearance from other bone cells.

• Bone Remodeling and Repair

  • It involves the processes of bone deposition or bone production done by osteoblasts and bone resorption done by osteoclasts, which break down old bone.
  • This is similar to the endochondral formation of bone when cartilage becomes ossified; osteoblasts, osteoclasts, and bone matrix are present.
  • Bone remodeling: The bony callus is then remodelled by osteoclasts and osteoblasts, with excess material on the exterior of the bone and within the medullary cavity being removed.

• Bone Development

  • Blood vessels invade the cavities, while osteoblasts and osteoclasts modify the calcified cartilage matrix into spongy bone.
  • Osteoclasts then break down some of the spongy bone to create a marrow, or medullary cavity, in the center of the diaphysis.

• Hormonal Control of Blood Calcium Levels

  • In the skeleton, PTH stimulates osteoclasts, which are cells that cause bone to be reabsorbed, releasing calcium from bone into the blood.
  • Calcitonin decreases blood calcium levels by inhibiting osteoclasts, stimulating osteoblasts, and stimulating calcium excretion by the kidneys.

• Connective Tissues: Bone, Adipose, and Blood

  • There are three types of cells in bone: osteoblasts, osteocytes, and osteoclasts.
  • Osteoclasts are active in breaking down bone for bone remodeling, providing access to calcium stored in tissues in order to release it into the blood.
  • Osteoclasts are usually found on the surface of the tissue.
  • Osteoclasts bore tunnels into the bone and osteocytes are found in the lacunae.

• Thyroid Gland

  • It acts in the bones to inhibit osteoclast activity and in the kidneys to stimulate excretion of calcium.

• Parathyroid Glands

  • First, PTH enhances reabsorption of calcium by the kidneys; it then stimulates osteoclast activity and inhibits osteoblast activity.

• Growth of Bone

  • Osteoclasts, cells that work to break down bone, resorb old bone that lines the medullary cavity.