Musculoskeletal System - Bone Development Timeline: Difference between revisions
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* '''An image-based skeletal tissue model for the ICRP reference newborn'''<ref><pubmed>19556686</pubmed> "Active marrow distributions were found to be in reasonable agreement with those given previously by the ICRP. However, significant differences were seen in total skeletal and site-specific masses of trabecular and cortical bone between the current and ICRP newborn skeletal tissue models. The latter utilizes an age-independent ratio of 80%/20% cortical and trabecular bone for the reference newborn. In the current study, a ratio closer to 40%/60% is used based upon newborn CT and micro-CT skeletal image analyses. These changes in mineral bone composition may have significant dosimetric implications when considering localized marrow dosimetry for radionuclides that target mineral bone in the newborn child." | * '''An image-based skeletal tissue model for the ICRP reference newborn'''<ref><pubmed>19556686</pubmed></ref> "Active marrow distributions were found to be in reasonable agreement with those given previously by the ICRP. However, significant differences were seen in total skeletal and site-specific masses of trabecular and cortical bone between the current and ICRP newborn skeletal tissue models. The latter utilizes an age-independent ratio of 80%/20% cortical and trabecular bone for the reference newborn. In the current study, a ratio closer to 40%/60% is used based upon newborn CT and micro-CT skeletal image analyses. These changes in mineral bone composition may have significant dosimetric implications when considering localized marrow dosimetry for radionuclides that target mineral bone in the newborn child." | ||
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Revision as of 17:57, 2 February 2011
Introduction
The adult human skeleton has about 206 different bones which are formed from fusion of significantly more bones in the postnatal developing neonate and child (about 275). Ossification in general continues postnatally, through puberty until mid 20s.
The two major parts of the human skeleton are the axial (80 bones in skull, vertebra, ribs, sternum) and appendicular (126 bones in limbs, shoulders, pelvis) skeletons.
These notes summarise the timecourse of development of some of these bones in humans.
Two main forms of ossification occur in different bones, intramembranous (eg skull) and endochondral (eg vertebra) ossification.
Endochondral ossification within the limb begins at Carnegie stage 18 and also occurs throughout embryo skeleton. This process is the replacement of a cartilage "template" with bone (week 5-12) that continues through postnatal development, with a second surge of growth at puberty.
Some Recent Findings
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Ossification Stages
The process of ossification as determined postnatally clinically has been divided into a series of stages.[2]
- Stage 1 - non-ossified epiphysis
- Stage 2 - discernible ossification centre
- Stage 3 - partial fusion
- Stage 4 - total fusion
- Stage 5 - an additional stage recently added is the disappearance of the epiphyseal scar after total fusion.
Clavicle Ossification
The following identifies the process of ossification of the medial clavicular epiphyseal cartilage.[3]
- Stage 3 - 16 years
- Stage 4 - 20 years (women), 21 years (men)
- Stage 5 - 26 years
Long Bone Ossification
Humerus
Appearance and fusion of bone secondary ossification centres, proximal is closer to body and distal is further away from the body.
Appearance
- Proximal epiphysis gestation week 36 - 4 years
- Distal epiphysis 6 months - 10 years
Fusion
- Proximal epiphysis 12 - 20 years
- Distal epiphysis 11 - 19 years
Femur
Appearance
- Proximal epiphysis 1 - 12 years
- Distal epiphysis Gestation week 36 - 40
Fusion
- Proximal epiphysis 11 - 19 years
- Distal epiphysis 14 - 19 years
Data from reference[4] Table 1.
Mandible Ossification
Prenatal
Week 6 - Intramembranous ossification center develops lateral to Meckel's cartilage.
Week 7 - Coronoid process begins differentiating.
Week 8 - Coronoid process fuses with main mandibular mass.
Week 10 (approx) - Both condylar and coronoid processes are recognizable and anterior portion of Meckel's cartilage begins to ossify.
Weeks 12-14 - Secondary cartilages for the condyle, coronoid, and symphysis appear.
Weeks 14-16 - Deciduous tooth germs start to form.
Birth
At birth mandible still has separate right and left halves.
Postnatal
Year 1 - Fusion of right and left halves of mandible at the symphysis.
Infancy and childhood - Increase in both size and shape of the mandible; eruption and replacement of teeth.
Year 12-14 - All permanent teeth emerged except third molars.
Data from reference[4] Table 4.
References
Online Textbooks
- Developmental Biology by Gilbert, Scott F. Sunderland (MA): Sinauer Associates, Inc.; c2000 Paraxial and intermediate mesoderm | Osteogenesis: The Development of Bones
- Molecular Biology of the Cell Alberts, Bruce; Johnson, Alexander; Lewis, Julian; Raff, Martin; Roberts, Keith; Walter, Peter New York and London: Garland Science; c2002 Search Molecular Biology of the CellBone Is Continually Remodeled by the Cells Within ItImage: Figure 22-52. Deposition of bone matrix by osteoblasts.Image: Figure 22-56. The development of a long bone.
Reviews
<pubmed>19092089</pubmed> <pubmed>18279783</pubmed>
Articles
<pubmed>14152896</pubmed>
Search PubMed
- Bone Development
Search Pubmed: Human Bone Development Timeline | Human Bone Development
External Links
External Links Notice - The dynamic nature of the internet may mean that some of these listed links may no longer function. If the link no longer works search the web with the link text or name. Links to any external commercial sites are provided for information purposes only and should never be considered an endorsement. UNSW Embryology is provided as an educational resource with no clinical information or commercial affiliation.
Glossary Links
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Cite this page: Hill, M.A. (2024, May 3) Embryology Musculoskeletal System - Bone Development Timeline. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Musculoskeletal_System_-_Bone_Development_Timeline
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G