Musculoskeletal System - Bone Development Timeline

Embryology - 19 Apr 2024        Expand to Translate
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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). Two main forms of ossification occur in different bones, intramembranous (eg skull) and endochondral (eg vertebra) ossification. Ossification in general continues postnatally, through puberty until mid 20s.

Axial skeleton (80 bones in skull, vertebra, ribs, sternum)

Appendicular skeleton (126 bones in limbs, shoulders, pelvis)

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.

These notes summarise the timecourse of development of some of these bones in humans.

Some Recent Findings

Primary ossification in the mouse limb.

An image-based skeletal tissue model for the ICRP reference newborn "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."

Ossification Stages

Epiphysis and epiphyseal disc.

The process of ossification as determined postnatally clinically has been divided into a series of stages.

• 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.

• 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 Table 1.

Historic Limb Data

Manual of Human Embryology by Franz Keibel and Franklin P. Mall (1910)

Table - Upper Limb

Upper Limb

Table Of Ossification Of The Bones Of The Superior Extremity

Bone	Centres	Time of appearance of centre	Union of primary and secondary centres; remarks.
Clavicle	Diaphysis	6th week	There are two centres in the shaft, a medial and a lateral. These blend on the 45th day (Mall). Shaft and epiphysis unite between the 20th and 25th years.
	Sternal epiphysis	18th to 20th year
Scapula	Primary centres:		The chief centre appears near the lateral angle. The subcoracoid centre appears at the base of the coracoid process and also gives rise to a part of the superior margin of the glenoid fossa. The coracoid process joins the body about the age of puberty. The acromial epiphysis centres (two or three in number) fuse with one another soon after their appearance and with the spine between the 22nd and 25th years (Quain); 20th year (Wilms). The subcoracoid and the epiphysis of the coracoid process, the glenoid fossa, the inferior angle, and the vertebral margin join between the 18th and 24th years in the order mentioned (Sappey).
	1. That of the body, the spine, and the base of the glenoid cavity.	8th week (Mall) 1
	2. Goraooid process	1st year
	3. Subcoracoid	10th to 12th year
	Epiphyses:
	Acromial epiphyses	15th to 18th year
	Epiphysis of the inferior angle.	16 to 18th year
	Epiphyses of the vertebral border.	18th to 20th year
	Epiphyses of upper surface of coracoid.	16th to 18th year.
	Epiphysis of surface of glenoid fossa.	16th to 18th year.
Humerus	Diaphysis	6th to 7th week (Mall)	The epiphyses of the head, the tuberculum majus and the tuberculum minus (the last is inconstant) unite with one another in 4th-6th year and with the shaft in 20th-25th year. The epiphyses of the capitulum, lateral epicondyle, and trochlea unite with one another and then in the 16th-17th year join the shaft. The epiphysis of the medial epicondyle joins the shaft in the 18th year.
	Epiphyses:
	Head	1st to 2d year
	Tuberculum majus	2d to 3d year
	Tuberculum minus	3d to 5th year
	Capitulum	2d to 3d year
	Epioondylus med	5th to 8th year
	Lateral margin of trochlea	11th to 12th year
	Epicondylus lat	12th to 14th year
Radius	Diaphysis	7th week (Mall)	The superior epiphysis and shaft unite between the 17th and 20th years. The inferior epiphysis and shaft about the 21st year (Pryor); M 21st year, F 21st-25th year (Sappey). Sometimes an epiphysis is found m the tuberosity (R. and K.) and in the styloid process (Sappey).
	Epiphyses:
	Carpal end	F 8th month - M 15th month (Pryor)
	Humeral end	6th-7th year
Ulna	Diaphysis	7th week	The centre for the shaft of the ulna arises a few days later than that for the radius. The proximal epiphysis is united to the shaft about the 17th year; the inferior epiphysis between the 18th and 20th years; F 20th - 21st years, M 21st - 24th years (Sappey). There is sometimes an epiphysis in the styloid process (Sohwegel) and in the tip of the olecranon process (Sappey).
	Epiphyses:
	Carpal end	F 6th-7th year - M 7th-8th year (Pryor)
	Humeral end	10th year
Carpus	Os capitatum	F 3d-6th month M 4th-10th month	The navicular sometimes has two centres of ossification (Serres. Rambaud and Renault). Serres and Pryor have described two centres of ossification in the lunatum. Debierre has described two centres in the pisiform, one in a girl of eleven, the other in a boy of twelve. The OS hamatum may have a special centre for the hamular process. Pryor has found two centres in the triquetrum. Pryor (1908), describes the centres of ossification of the carpal bones as assuming shapes characteristic of each bone at an early period.
	Os hamatum	F 5th-10th month M 6th-12th month
	Os triquetrum	F 2d-3d year M about 3 years
	Os lunatum	F 3rd-4th year M about 4 years
	Os naviculare	F at 4 years, or early in 5th year M about 5 years
	Os mult. maj.	F 4th-5th year M 5th-6th year
	Osmult. min.	F 4th-5th year M 6th-6th year
	Os pisiforme	F 9th-10th year M 12th-3th year
Metacarpals	Diaphyses	9th week (Mall)	The centres for the shafts of the second and third metacarpals are the first to appear. There may be a distal epiphysis for the first metacarpal and a proximal epiphysis for the second. Pryor (1906). found the distal epiphysis of the first metacarpal in about 6 per cent, of cases. It is a family characteristic. It arises before the 4th year and unites later. Pryor found the proximal epiphysis of the second metacarpal in six out of two hundred families. It unites with the shaft between the 4th and 6th-7th year; sometimes, however, not until the 14th year. In the seal and some other animals all the metacarpals have proximal and distal epiphyses (Quain). The epiphyses join the shafts between the 15th and 20th years. There may bean independent epiphysis for the styloid process of the 5th metacarpal. The epiphysis of the metacarpal of the index finger appears first. This is followed by those of the 3d, 4th, 5th, and 1st digits.
	Proximal epiphysis of the first metacarpal	3d year
	Distal epiphyses of the metacarpals	2d year
Phalanges	Diaphyses	9th week (Mall)
First row	Proximal epiphyses	1st-3rd year (Pryor)	The shafts of the phalanges of the second and third fingers are the first to show centres of ossification. The phalanges of the little finger are the last, the epiphysis in the middle finger is the first to appear. This is followed by those of the 4th, 2d, 5th, and 1st digits.
Middle row	Diaphyses	11th-12th week (Mall)	The centres in the shafts of this row are the last to appear. The epiphysis of the phalanx of the middle finger is the first to appear. This is followed by those of the ring, index, and little finger (Pryor).
	Proximal epiphyses	2nd-3rd year
Terminal row	Diaphyses	7th-8th week	The terminal phalanx of the thumb is the first to show a centre of ossification in the shaft. This is the first centre of ossification in the hand. It is developed in connective tissue while the centres of the other phalanges are developed in cartilage (Mall). The epiphysis of the ungual phalanx of the thumb is followed by those of the middle, ring, index, and little fingers. The fusion of the epiphyses of the phalanges with the diaphyses takes place in the 18th-20th year.
	Proximal epiphyses	2nd-3rd year
Sesamoid bones			Ossification begins generally in the 13th - 14th years, and may not take place until after middle life (Thilenius). For table of relative frequency in the embryo and adult see p. 385.
Days and weeks refer to the prenatal, years to the postnatal period. M = male F = female. According to Poirier, Traite d'Anatomie, p. 138, two centres appear in the eighth week, and unite in the third month to form a centre of ossification for the body of the scapula.
Links: limb | bone | upper limb ossification timeline | lower limb ossification timeline | Historic - Chapter 11 Development of the Skeleton | timeline | Category:Timeline     Table Data Reference

Hip

Ossification of the Os Coxae

• Triradiate cartilage 14 - 16 years.
  • Y-shaped growth plate region within the developing hip seen in childhood x-rays.

Links: Musculoskeletal System - Abnormalities

Mandible Ossification

Fetal week 12

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.

• 

  Embryo CRL 24 mm (outer aspect, about Carnegie stage 22)

• 

  Embryo CRL 24 mm (inner aspect, about Carnegie stage 22)

• 

  Embryo CRL 95 mm (outer aspect, about Fetal week 12, GA week 14)

• 

  Embryo CRL 95 mm (inner aspectt, about Fetal week 12, GA week 14)

Birth

Adult Mandible, muscle attachment sites

At birth mandible still has separate right and left halves.

• 

  Birth

• 

  Childhood

• 

  Adult

• 

  Old Age

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 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.

Terms

• growth recovery lines (growth arrest lines, Harris lines, Parks lines) - lines visible on x-ray images of increased bone density that represent the position of the growth plate at the time of insult to the organism and formed on long bones due to growth arrest. Insults can include juvenile malnutrition, disease or trauma.

Glossary Links

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Cite this page: Hill, M.A. (2024, April 19) Embryology Musculoskeletal System - Bone Development Timeline. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Musculoskeletal_System_-_Bone_Development_Timeline

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G