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26 Cards in this Set

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  • Back
mesenchymal origins of axial skeleton and musculature(4)
2)intermediate mesenchime (nephrotome):kidney
3)lateral plate mesenchyme
4)notochord - nucleus pulposus of intervertebral disk
derivitives of somites(3)and what they become
1)dermatome- dermis of skin
2) myotome - skeletal mm
3)sclerotome - vertebrae, disc (annulus fibrosis, & ribs
what makes up the lateral plate of the mesenchyme and what does it become
1) splanchnopleure - smoothmuscle of gut
2) somatopleure - appendicular skeleton and vasculature
intramembraneous bone development
primarily in skull
intracartilagenous, most bones except the skull
describe bone bone formation from 4th week on
4th week - mesenchyme migrates to area
5th week mesenchyme condences
6th week - chondrification
7-12 weeks - ossification of primary centers
bith to 9nd year - ossification of secondary centations and formation of epiphyseal plates
18th-25th year - fusion of epiphyseal plates and end of bone growth
Development of vertebrae
Vertebrae arise from sclerotome, which is the most medial part of the somite.
Each vertebral segment derives from a part of two separate somites.
These come together to form a single vertebra.
The intervertebral disk derives from mesoderm remaining behind after mesodermal migration.
spinal bifida
late closure of caudal neuropore results in delay of inductive signal for neural arch, until the point where mesenchyme is not responsive to such a signal (hence, no neural arch forms)
failure of sclerotome to divide and migrate resultin gin an abnormal vertebral segment -- scholiosis
origin of body wall musculature
myotomes (of somite)
how do myotomes differentiate
they differentiate into myoblasts during emryonic period which fuses to form skeletal mm in fetal division
2 primary devisions of dermomyotome
exclusively myotome - forms deep back mm and is innervated by dorsal rami of spinal nerves
from dermatome portion of dermomyotome - travels adjacent to somatopleure and contributes to appendicular and body wall musculature. it is innervated by ventral rami of spinal nn
what is the pattern of nn mm association
myoblasts develop 1st in the 4th-5th week. Axons then grow out of CNS in 5th week and follow the migrating myoblasts. Axons divide into preaxial (flexor) and postaxial (extensor) groups of mm. Axons begin migration to their final location during the 5th to 6th week. Aroudn the 17th -10th week. mm begin to function and we see movement of limbs. Around 2 years postanat you have myelination of lower extremities.
Hypaxial myoblasts differentiate themselves from epaxial by a process called _________
developemnt of upper limb of appendicular skeleton occers in a ___________ rotation
lateral (outward)
developemnt of lower limb of appendicular skeleton occers in a ___________ rotation
medial (inward)
preaxial (fx, innervation)
flexors, ventral
postaxial (fx, innervation)
extensors, dorsal
fusion of digits (failure of appropriate cell death)
extra digits (abnormal induction of a 6th digit)
absense of a limb
absence of part of a limb
lobster-claw hand
absence of 3rd digit, fusion of 4th & fith
hypomere mesoderm migrates ______ to somatopleure
superficial ( so mm superficial to bone)