Osteoclast
Definition
The large, multinucleated bone-resorbing cell responsible for excavating the resorption tunnel in a BMU. Activated by the RANKL/OPG cytokine axis. Creates the space that osteoblasts subsequently fill with new lamellar bone.
- Cell type
- Large, multinucleated bone-resorbing cell
- Function
- Excavates the resorption tunnel in a BMU
- Regulation
- RANKL/OPG cytokine axis
- Downstream effect
- Creates space osteoblasts later fill with new bone
Common questions
Why does osteoclast activity matter for forensic age or PMI estimation?+
The rate and pattern of bone remodeling driven by osteoclasts shapes osteon density and turnover, features that histological age estimation methods measure in a cross-section of cortical bone.
Are osteoclasts and osteoblasts the same cell type at different stages?+
No, they are distinct lineages. Osteoclasts derive from monocyte precursors and resorb bone, while osteoblasts derive from mesenchymal stem cells and deposit new bone; the two act in a coupled but separate sequence within a BMU.
Related terms
- Cortical (Compact) Bone
- The dense outer shell of long bones and the tables of flat bones. Approximately 80% of skeletal mass. High mineral density (65-70%...
- Epiphyseal Growth Plate (Physis)
- The cartilaginous zone between the epiphysis and metaphysis where endochondral ossification occurs during growth. Closes (fuses) at puberty under the influence of...
- Haversian System (Secondary Osteon)
- The basic structural unit of mature cortical bone: a cylinder of 4-20 concentric lamellar rings around a central Haversian canal carrying blood...
- Interstitial Lamellae
- The angular remnants of older osteons left behind after a BMU has partially resorbed them. Their relative area decreases with age as...
- Kerley Method
- A histological age estimation method published by Ellis Kerley in 1965, based on counting secondary osteons, osteon fragments, circumferential lamellar bone, and...
- Lacuna
- A small lens-shaped cavity within bone lamellae that houses an osteocyte cell body. Lacunae are connected by canaliculi radiating toward the Haversian...
- Plexiform Bone
- A microstructural pattern found in the cortical bone of large rapid-growth mammals (bovids, horses, deer) characterised by alternating layers of woven bone...
- Trabecular (Cancellous) Bone
- The porous, lattice-like interior bone occupying epiphyses, metaphyses, and flat bones. High surface area and metabolic activity but rapidly lost in taphonomic...
- Wolff's Law
- The principle that bone is deposited and resorbed in response to mechanical loading history. Cortical thickness and trabecular orientation follow principal stress...