Osteoid

Osteoid is the unmineralized, organic portion of the bone matrix that forms prior to the maturation of bone tissue. It is produced by osteoblasts and is composed primarily of collagen, proteoglycans, and non-collagenous proteins. Osteoid makes up about 50% of bone volume and 40% of bone weight.

Composition

Osteoid is composed of approximately 90% collagen (mostly type I collagen) and 10% non-collagenous proteins. The non-collagenous proteins include osteocalcin, osteopontin, bone sialoprotein, and bone proteoglycan. These proteins play a crucial role in the mineralization of the osteoid matrix.

Function

The primary function of osteoid is to provide a framework for the deposition of calcium and phosphate ions, which form hydroxyapatite crystals. This process, known as mineralization, gives bone its hardness and strength. Osteoid also plays a role in bone remodeling, a process in which old bone is broken down and new bone is formed.

Clinical significance

Abnormalities in osteoid can lead to various bone disorders. For example, rickets and osteomalacia are caused by a deficiency in mineralization, resulting in an excess of osteoid. Osteogenesis imperfecta, a genetic disorder, is caused by defects in the collagen found in osteoid.

See also

• Bone tissue
• Osteoblast
• Osteocyte
• Osteoclast
• Osteogenesis
• Bone remodeling

Osteoid Resources
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