Musculoskeletal System - Bone Development Timeline: Difference between revisions

Revision as of 17:56, 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.

Historic Embryology - Musculoskeletal
1853 Bone \| 1885 Sphenoid \| 1902 - Pubo-femoral Region \| Spinal Column and Back \| Body Segmentation \| Cranium \| Body Wall, Ribs, and Sternum \| Limbs \| 1901 - Limbs \| 1902 - Arm Development \| 1906 Human Embryo Ossification \| 1906 Lower limb Nerves and Muscle \| 1907 - Muscular System \| Skeleton and Limbs \| 1908 Vertebra \| 1908 Cervical Vertebra \| 1909 Mandible \| 1910 - Skeleton and Connective Tissues \| Muscular System \| Coelom and Diaphragm \| 1913 Clavicle \| 1920 Clavicle \| 1921 - External body form \| Connective tissues and skeletal \| Muscular \| Diaphragm \| 1929 Rat Somite \| 1932 Pelvis \| 1940 Synovial Joints \| 1943 Human Embryonic, Fetal and Circumnatal Skeleton \| 1947 Joints \| 1949 Cartilage and Bone \| 1957 Chondrification Hands and Feet \| 1968 Knee

Some Recent Findings

An image-based skeletal tissue model for the ICRP reference newbornCite error: Closing </ref> missing for <ref> tag

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.^[1]

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^[2] 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^[2] Table 4.

References

↑ <pubmed>14534796</pubmed>
↑ ^2.0 ^2.1 <pubmed>12866701</pubmed>

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 Cell Bone Is Continually Remodeled by the Cells Within It Image: Figure 22-52. Deposition of bone matrix by osteoblasts.Image: Figure 22-56. The development of a long bone.

Reviews

Articles

Search PubMed

Bone Development

Search Pubmed: Human Bone Development Timeline | Human Bone Development

External Links

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Cite this page: Hill, M.A. (2026, August 16) Embryology Musculoskeletal System - Bone Development Timeline. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Musculoskeletal_System_-_Bone_Development_Timeline

What Links Here?

[1] <pubmed>14534796</pubmed>

[PMID12866701-2] 2.0 ^2.1 <pubmed>12866701</pubmed>

[1]

[2]

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-* An image-based skeletal tissue model for the ICRP reference newborn19556686 "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> "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."
 |}