Musculoskeletal development

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Pharynx and Craniofacial Development | Main Anatomy Index | Neuroembryology

Last updated 30 March 2006

This page was contributed by David Boshell

Musculoskeletal Development

Early differentiation

  1. Cylindrical, paraxial mesoderm, just lateral to the notochord
  2. Less pronounced, slenderer intermediate mesoderm, lateral to the paraxial mesoderm
  3. A flat sheet of lateral plate mesoderm, filling the remainder of the disc

 

The paraxial mesoderm

Segmental organisation of the body

7

Cranial somitomeres

4

Occipital somites

8

Cervical somites

12

Thoracic somites

5

Lumbar somites

5

Sacral somites

3

Coccygeal somites

Differentiation of the somites

  1. The sclerotome medially, that migrates to surround the developing notochord and neural tube
  2. The dermamyotome that is displaced laterally, and will itself split into:

 

Formation of the vertebrae

Segmental organisation of the vertebrae

7

Cervical vertebrae

12

Thoracic vertebrae

5

Lumbar vertebrae

5

Sacral vertebrae

3

Coccygeal vertebrae

 

Development of the thorax

 

Differentiation of the dermamyotomes

  1. A dorsal epimere, that will form the deep muscles of the back (erector spinae etc.)
  2. A ventral hypomere that will form the anterolateral thoracic and abdominal wall muscles
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Development of the limbs

 

Limb bud differentiation

Time period

Distinguishable features

Day 33

Hand plate, forearm and shoulder regions

Day 37

Thigh, leg and foot regions

Day 38

Finger rays in hand plate

Day 44

Toe rays in foot plate

Day 52

Limbs have rotated from coronal to parasagittal orientation, feet and hands meet at midline

Day 57

Limbs well defined
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Bone development

  1. Endochondral ossification
  2. Membranous ossification
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Michael Tam (c) 1999