Musculoskeletal Development Flashcards
embryonic sources of skeletal system
- paraxial mesoderm (somites)
- lateral plate mesoderm
- neural crest cells
paraxial mesoderm deriviatives
mesenchyme -> vertebral column, ribs, neruocranium, annulus fibrosis
lateral plate mesoderm derivatives
mesenchyme -> pectoral girdle, pelvic girdle, limbs, sternum
neural crest cell derivatives
mesenchyme -> viscerocranium and hyoid bone
what forms all of the axial skeleton except sternum and portion of skull?
sclerotome
what occurs for vertebral development i nthe 4th week?
sclerotome cells surround neural tube and notocord
what are the portions that will for vertebra?
less dense cranial portion and dense caudal portion
how do the portions of the vertebra fuse?
dense portions (forms annulus fibrosis), fuses with less dnese portion immediately inferior to form vertebral body
sclerotome resegmentation
6th week: chondrification
7th week: ossification
rib development
grows out as lateral extensions of coastal processes developing from thoracic vertebrae and wrap around anteriorly
synovial joints form where costal processes and vertebrae meet
sternum development
induced to form form ribs at ventral midline from lateral plate somatic mesoderm
week 10: develops as two bars that fuse cranial to caudal
what are the two parts of the skull and what are they formed from?
- viscerocranium: neural crest cells
2. neurocranium: paraxial mesoderm (occipital somites form portion)
what skull bones form from endochondral ossification?
sphenoid, petrous part of temporal bone, portion of occipital bone
what skull bones form from intramembranous ossification?
all other bones (flat bones surrounding brain)
what are sutures?
membranous and flexible joints in infants
what are fontanelles?
enlarged membranous spaces where more than two bones meet
anterior, posterior, sphenoidal, mastoid
what does the appendicular skeleton from from?
lateral plate somatic mesoderm
what type of bone development occurs in the appendicular skeleton?
endochondral ossification
what occurs during the 5th week of appendicular skeleton development?
condensations of mesenchyme appear in limb buds
what occurs during the 6th week of appendicular skeleton development?
mesenchymal bone models undergo chondrification to form hyaline cartilage models
what occurs during the 7/8th week of appendicular skeleton development?
ossification begins in long bones, initially in diaphysis at primary ossification centers
when do the epiphyses of long bones ossify?
after birth
what are the embryologic origins of the 3 types of muscle?
skeletal: paraxial mesoderm
cardiac: intraembryonic splanchnic mesoderm
smooth: intraembryonic splanchnic mesoderm
what do somites differentiate into in skeletal muscle development?
- sclerotome
- myotome
- dermatome
what do somites give rise to?
most of axial skeleton, musculature, dermis of back
myoblasts?
specialized mesoderm cells that fuse together to form skeletal m. and can actively contract by week 7
what are progenitor cells for muscle derived from?
- ventrolateral lips of dermomyotome
2. dorsomedial lips of dermomyotome
what separates paraxial from lateral plate somatic mesoderm?
lateral somitic frontier
what are the two domains in somites?
- primaxial domain
2. abaxial domain
where is the primaxial domain?
surrounding neural tube, dorsomedial lip, and some ventrolateral lip
what forms from the primaxial domain?
- musculature of back
- shoulder girdle
- intercostal mm.
where is the abaxial domain?
parietal layer of lateral plate mesoderm, most ventrolateral lip cells crossing frontier into lateral plate mesoderm
what forms from abaxial domain?
- infrahyoid mm
- pec major and minor
- abdominal wall mm
- limb mm
what does the primaxial domain become?
epaxial group
what does the abpaxial domain become?
hypaxial group
what does each myotome divide into?
- epaxial group: dorsal/posterior
2. hypaxial group: ventral/anterior
what does each spinal nerve divide into?
- dorsal primary ramus (epaxial mm)
- ventral primary ramus (hypaxial mm)
*vent divides to form dorsal/ventral brs to compartments
what does the intraembryonic splanchnic mesoderm of cardiac m give rise to?
mesenchyme surrounding developing heart tube
what does the intraembryonic splanchnic mesoderm of smooth m give rise to?
wall of gut and gut tube, most large arteries
what are the two ectoderm derivatives of SM?
- neuroectoderm
2. surface ectoderm
what derives from neuroectoderm?
sphincter pupillae m and dilator pupillae m of iris
what derives from surface ectoderm?
myoepithelial cells of mammary, salivary, and sweat glands
what happens in limb development at end of week 4
buds emerge, UL first, LL 1-2 days later
limb bud
core of mesenchyme (forms CT of limb), lines with surface ectoderm
what is the progress zone?
area of limb bud that keeps cells undifferentiated and rapidly dividing
what sends signaling factor to nearby mesenchyme of progress zone
apical ectodermal ridge
what is the direction of limb growth?
proximal to distal
what are the migratory cells that invade limb buds?
- melanocytes: from neural crest
- sensory axons and schwann cells: from NC
- myoblasts: from myotome of VLL
- motor axons: from neural tube
limb rotation
weeks 7
UL rotates 90 laterally
LL rotates 90 medially
meromelia
absence of part of limb
amelia
absence of entire limb
polydactyly
extra digits
syndactyly
2 or more fused digits
