Limb Development Flashcards
musculature is derived from what portion of the mesoderm
paraxial mesoderm –> myotome
bones are derived from what portion of the mesoderm
lateral plate mesoderm - somatic region
tendons are derived form what portion of the mesoderm
lateral plate mesoderm
somatic region
during the fourth week
both limb buds appear
upper - 24 days
lower - 28 days
during the fifth week, limb development
has reached hand/foot plate development
chondrificaiton occurs
during the sixth week, limb development has reached the stage of
digital rays of hands
limb skeleton is cartilaginous
during the seventh week, limb development has reached the stage of
digital rays of feet have formed
osteogenesis begins
limbs begin to rotate
during the 8th week the limb begins to
form separate digits using BMP signaling (induces cell apoptosis)
by the 12th week of development, the limbs are undergoing
primary ossification
Fgf10 from mesenchyme is responsible for what signaling
activates WNT
WNT induces other Fgfs
sets up positive feedback loop FGF–> WNT–>FGF–>WNT
sets up primary gradient
Apical ectodermal ridge controls which axis
proximal/distal axis
AER responsible for continued outgrowth
secretes Fgf8
Fgf8 is primarily secreted by
the Apical ectodermal ridge (AER)
Fgf8 is a key regulator of _______ and interacts with ______
key regulator of distal outgrowth
interacts with Fgf10
hox gene expression pattern correlates with
identity elements along proximal distal axis
9-10 –> styolopod
11 –> zeugopod
12-13 –> autopod
Zone of polarizing activity controls what axis development
controls AP axis
induced by Shh activity
Shh is associated with the ______ to designate which axis
zone of polarizing activity AP axis (pinky vs thumb)
paralog
gene related to each other due to descent from a common ancestral DNA sequence (commonly duplication)
AP axis specification occurs even before
limb bud outgrowth
grafting Shh onto the anterior portion of a growing limb bud will result in
mirrored medial digits (more pinkies)
primary molecular regulator of dorsal/ventral axis
Wnt7a controlled by Lmx1b
Wnt7a activity is associated with which surface of distal limb
Wnt7a does dorsalization
BMP controls what process of limb development
formation of digits through apoptosis
dorsal mass forms ______ and _____ of upper limb but forms the ________ and _______ of lower limb
dorsal
extensors and supinators of upper
extensors and abductors of lower
ventral mass forms ______ and ______ of upper limb but forms the _______ and _______ of lower limb
ventral
flexors and pronators of upper limb
flexors and adductors of lower limb
limb rotation occurs as a result of
torsion in femoral/humeral diaphysis
upper extremity rotates _________, making the flexor compartment face _____ and extensors ______
upper extremity rotates 90 laterally, flexor compartment faces anteriorly and extensors are posterior
lower extremity rotates _________, making the flexors face ______ and the extensors face ______
lower extremity rotates 90 medially, flexors are posterior and extensors are anterior
limb rotation begins at week
7
sensory axons follow what structure to innervate the muscles
sensory axons follow the efferent axons from the ventral rami innervating the limb muscles
limb musculature is derived from
dorsolateral cells of the somites
Lmx1b turns on
Wnt7a
sorting of innervation, cranial and caudal
axons cranial to limb innervate dorsal musculature
axons caudal to limb innervate ventrocaudal musculature
axial arteries in upper and lower limb develop _________ at __ and __ days post fert, respectively
develop de novo
30 days in upper
36 dpf in lower
vasculature for limbs involves remodeling of what structures
7th cervical intersegmental a
5th lumbar intersegmental a
Originate within surrounding mesoderm and join dorsal aorta - branch to join axial artery
late/partial loss of FGF signaling results in
meromelia
absence of part of a limb
early loss of FGF signaling results in
amelia
total absence of entire limb
overexpression of Shh can result in
polydactyly - presence of supernumerary digits
forms second ZPA
extra digit lacks normal musculature
usually most medial/lateral digit is duplicated
adactyly is a total
absence of digits
cutaneous syndactyly
simple webbing of digits .
osseous syndactyly
fusion of bones, digital rays fail to develop
BMP disruption or HoxD13 mutation
Thalidomide exposure resulted in this melia
phacomelia - absence of long bones with rudimentary hands and feet
partial loss of FGF siglaning or Hox disruption
FGF8 signaling defects would result in
ectrodactyly/lobster claw deformity - split hand/foot anomaly
amnion adhering to fetal structures results in
deletion of those structures
amniotic bands?
Bilateral talipes equinovarus
club foot
results from oligohydramnios (deficiency of amniotic fluid) reducing fetal movements
