Osteoid

Osteoid
Osteoid
	Light micrograph of osteoid, containing two osteocytes, being synthesized by osteoblasts.
Identifiers
FMA	66830
	Anatomical terminology [edit on Wikidata]

In histology, osteoid is the unmineralized, organic portion of the bone matrix that forms prior to the maturation of bone tissue.^[1] Osteoblasts begin the process of forming bone tissue by secreting the osteoid as several specific proteins. The osteoid and its adjacent bone cells have developed into new bone tissue when it becomes mineralized.

Osteoid makes up about fifty percent of bone volume and forty percent of bone weight. It is composed of fibers and ground substance. The predominant type of fiber is type I collagen and comprises ninety percent of the osteoid. The ground substance is mostly made up of chondroitin sulfate and osteocalcin.

Disorders

When there are insufficient nutrient minerals or osteoblast dysfunction, the osteoid does not mineralize properly and accumulates. The resultant disorder is termed rickets in children and osteomalacia in adults. A deficiency of type I collagen, such as in osteogenesis imperfecta, also leads to defective osteoid and brittle, fracture-prone bones.

In some cases, secondary hyperparathyroidism can cause a disturbance in mineralisation of calcium and phosphate.

Another condition is a disturbance in primitive transformed cells of mesenchymal origin, which exhibit osteoblastic differentiation and produce malignant osteoid. This results in the formation of a malignant primary bone tumor known as osteosarcoma or osteogenic sarcoma. This malignancy most often develops in adolescence during periods of rapid osteoid formation (commonly referred to as growth spurts).^[2]

References

^ Trammell, Lindsay H.; Kroman, Anne M. (2013-01-01), DiGangi, Elizabeth A.; Moore, Megan K. (eds.), "Chapter 13 - Bone and Dental Histology", Research Methods in Human Skeletal Biology, Academic Press, pp. 361–395, doi:10.1016/b978-0-12-385189-5.00013-3, ISBN 978-0-12-385189-5, retrieved 2020-11-18
^ Ottaviani Giulia; Jaffe Norman (2009). "The Epidemiology of Osteosarcoma". Pediatric and Adolescent Osteosarcoma. Cancer Treatment and Research. Vol. 152. New York: Springer. pp. 3–13. doi:10.1007/978-1-4419-0284-9_1. ISBN 978-1-4419-0283-2. PMID 20213383.

Netter, Frank H. (1987), Musculoskeletal system: anatomy, physiology, and metabolic disorders, Summit, New Jersey: Ciba-Geigy Corporation
Jaffe, N.; et al. (2009). Pediatric and Adolescent Osteosarcoma. New York: Springer. ISBN 978-1-4419-0283-2.

External links

Histology image: 69_03 at the University of Oklahoma Health Sciences Center - "Bone, femur"
Dr. Susan Ott's website on osteomalacia

[1] Trammell, Lindsay H.; Kroman, Anne M. (2013-01-01), DiGangi, Elizabeth A.; Moore, Megan K. (eds.), "Chapter 13 - Bone and Dental Histology", Research Methods in Human Skeletal Biology, Academic Press, pp. 361–395, doi:10.1016/b978-0-12-385189-5.00013-3, ISBN 978-0-12-385189-5, retrieved 2020-11-18

[2] Ottaviani Giulia; Jaffe Norman (2009). "The Epidemiology of Osteosarcoma". Pediatric and Adolescent Osteosarcoma. Cancer Treatment and Research. Vol. 152. New York: Springer. pp. 3–13. doi:10.1007/978-1-4419-0284-9_1. ISBN 978-1-4419-0283-2. PMID 20213383.

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