Musculoskeletal

Musculoskeletal

1. Mesoderm

   • paraxial
   • Intermediate
   • Lateral plate

2. umbilical ring (28 days)

   • vitelline duct
   • umbilical cord
   • allantois

3. molecular signals for regulating somite differentiation come from surrounding tissues

   • sclerotome
     • vertebrae
       • HOX genes pattern the vertebrae and other bones
         • regulated by retanoic acid (vitamin A)
     • ribs
     • connective tissue
   • dermatome
     • dermis of the back
   • myotome
     • derived from both muscle forming regions
       • ventrolateral lip
       • dorsomedial lip

4. lateral somitic frontier

   • separates two mesodermal domains
     • paraxial mesoderm
       • around neural tube
         • give structure to backbone
       • derived only from somites
       • help make myotome
     • abaxial mesoderm
       • consists of
         • parietal layer of lateral plate mesoderm
         • mesoderm cells from somites
           • migrate across frontier

5. primaxial muscles

   • back muscles (extensors and rotators
   • intercostals
   • shoulder girdle (rhomboids, levator scapulae, latissimus dorsi)

6. abaxial muscles

   • abdominal (obliques and transversus abdominus)
   • distal upper limb
   • all lower limb

7. poland sequence

   • loss of pectoralis minor and part of major
     • usually unilateral

8. prune belly syndrome

   • lack of muscle cell migration

9. skull

   • neurocranium (encases brain
     • membranous neurocranium (flat bones)
     • cartilaginous neurocranium
       • chondrocranium (base of skull)
         • prechordal
           • neural crest cells
         • chordal
           • paraxial mesoderm (somitomeres)
             • myotomes
               • somitomeres
                 • head musculature
                   • tongue, eye, and pharyngeal arches
               • forms by cells at
                 • ventrolateral lip (VLL)
                   • contributes cells to both primaxial and abaxial domains of mesoderm
                 • dorsomedial lip (DML)
                   • contributes cells to primaxial domain of mesoderm (and sclerotome and dermatome cells)
               • somites
     • from neural crest cells and somitomeres
   • viscerocranium (face)
     • entirely neural crest
   • craniosynostosis
     • premature closure of one or more cranial sutures
     • scaphocephaly (sagittal suture)
     • brachycephaly and plagiocephaly (coronal sutures)
     • cloverleaf skull (all)