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40 Cards in this Set

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mesenchymal origins are derivitives of the _______
SOMITES
they are under influences of
SSH, BMP4, WNT
SSH influences
somatopleure
BMP-4 influences
hypaxial mm
WNT influences
epaxial mm
DERMOMYOTOME developes into
dermis of skin and skeletal mm
SCLEROTOME developes into
vertebrae, ANNULUS FIBROSIS of disk and ribs
Intermediate mesenchyme (NEPHROTOME) developes into
kidney
Lateral plate mesenchyme develops into these 2 things
1) SPLANCHNOPLEURE
2) SOMATOPLEURE
SPLANCHOPLEURE develops into
smoothe mm of gut
SOMATOPLEURE develops into
appendicular skeleton and vasculature
NOTOCHORD develops into
NUCLEUS PULPOSIS of intervertebral disk
intramembraneous bone
predominantly in scull (maybe clavical)
endochondral
intracartilagenous development ( most bones other than skull)
condensations of mesenchyme usually precedes what
endochondral and intra-membranous bone formation
condensantion of mesenchyme --6 steps
1) mesencym migrates to area (4th week)
2) condensation of mesenchyme (5th week)
3)CHONDRIFICATION (formation of cartilage) (6th week)
4) begin OSSIFICATION OF PRIMARY CENTERS (wk 7-12)
5) begin ossification of secondary centers and formation of epiphysieal plates (birth to 9y/o)
6) Fusion of EPIPHYSEAL PLATES and end of bone growth, usually 18-25 y/o)
patterns of development of joints
1) basic embryoic plan
2) development of SYNOVIAL JOINTS
3) development of FIBROCART/FIBROUS JTS
develpment of vert & intervvert discs
1) each segment develps from parts of 2 SCLEROTOMES (note pattern)
2)CHONDRIFICATION OF PRIMARY OSSIFICATION CENTERS
development of sacrum
1. union of 5 vert segments
2. all elements (costal part, vertebral arch, centrum0 develop from separate cartilaginous models
3. bony vert arch fuses w/ transverse processes at 2-5 y postnatal. these unite w/ bony centrum at 8 years
4. epiphyseal plates between sacral segments fuse sequentially after puberty, with lowest segments fusing first
spinal bifida
late closure of caudal neuropore results in delay of inductive signal for neural arch until the point where the mesenchyme is not responsive to such a signal (hense, no neural arch forms).
hemivertebra
failure of sclerotome to divide and migrate, resulting in abnormal vertebral segment
origins of body wall musculature
undifferentiated somites change to dermomyotome (under dorsal influence of Wnts & BMP-4). At the same time, the more ventral sclerotome differentiates under the ventral influence of shh (from the notochord) The mesodermal cells of the DERMOMYOTOME (in the head region called the somitomere) differentiate into MYOBLASTS (embryonic period) which fuse to form skeletal mm during the fetal period. The dermotome splits off a group of cells between the dermomyotome and the sclerotome, originally called the 'myotome'
primary divisions of embryonic musculature
epaxial and hypaxial
EPAXIAL
'myotome' origin. Deep back mm, innervated by dorsal rami of spinal nn
HYPAXIAL
'dermotome' origin: migrates outside of the blastimal skeleton form SOMATOPLEURE, contributes with appendicular and body wall musculature. Innervated by ventral rami of spinal nn
pattern of nn mm association
1) myoblasts develop (4th-5th week)
2)axons grow out of CNS in 5th week and follow migrating myoblasts.
3) Axons divide into preaxial (flexor) and postaxial (extensor) groups of mm
4) Axons begin migration to final location during 5th to 6th week.
5. Around 17th -20th week, mm begin to fx and you will see mvmt of limbs
6. Around 2 yrs postnatal, myelination of lower extremities
Development of mm fibers
1. elongated, elongated migrating embryonic myoblasts find their final locations and fuse into multinucliate primary and secondary myotubes
2. the myotubes develop myofilaments and become striated, becoming mm fibers
Apppendicular skeleton: general pattern of development
posterior part of limb bud developes sonic hedgehog gene for posterior bone sxs, and this gene is progressively expressed more anteriorly.
Upper limb has ______ rotation
LATERAL (OUTWARD)
in upper limb, cells migrating anterior to axis of limb are under _______ innervation
PREAXIAL (flexor; ventral)
in upper limb, cells migrating posterior to axis of limb are under _______ innervation
POSTAXIAL (extensor; dorsal) innervation

(NB-migration can change fx w/o changing innervation e.g., brachioradialis)
general patterns in upper limb developemnt
once myoblasts migrate into area, they separate into superficial and deep groups (if appropriate), and then into horizontal groups (e.g., extensor crpi ulnaris, extensor digitorum, extensor carpi radialis).

Proximal parts of the limb develop first, distal parts develop later
syndactily
fusion of digits (failure of appropriate cell death
polydactily
extra digit (abnormal induction of a 6th digit)
Amlia
absense of a limb
meromelia
absence of part of a limb
lobster claw hand
absence of the 3rd digit, fusion of 4th and 5th
lower limb general pattern of mm development is similar to upper limb with only minor differences T/F
T
Lower limb has _________ rotation
MEDIAL (INWARD) ROTATION

changes in position will alter relative location of preaxial and postaxial mm for leg
malformations of lower limb are similar to those of uppper limb-- give two notable exceptions
1. CLUB FOOT
2. congenitally dislocated hip (CDH)