Bone cells - Osteoblasts
Osteoblasts are large, plump cells that lie on bony surfaces and secrete the organic components of the extracellular matrix, ground substance and collagen fibers. They occur in the endosteum and are also located on the external surfaces of bone associated with the innermost layer of the periosteum. 600x, 600x
Osteoblasts >
Osteoblasts secrete osteoid, eventually surrounding themselves in the process. Once entirely enclosed by matrix, these cells are called osteocytes.
- Osteoblasts becoming osteocytes
Osteoblasts secrete osteoid, eventually surrounding themselves in the process. Once entirely enclosed by matrix, these cells are called osteocytes.
Osteoid >
Osteoid is composed of ground substance (mostly proteoglycans) and collagen fibers. It appears as a pale band lying on the bone surface beneath the osteoblasts. Osteoid rapidly becomes mineralized with calcium phosphate (hydroxyapatite).
Osteocytes >
Osteocytes maintain the matrix and are located in small spaces in the matrix called lacunae.
Lining cells >
Flattened, bone-lining cells are present on the surface of bone where no active growth or resorption is occurring.
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