Limb Development Flashcards

1
Q

musculature is derived from what portion of the mesoderm

A

paraxial mesoderm –> myotome

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2
Q

bones are derived from what portion of the mesoderm

A

lateral plate mesoderm - somatic region

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3
Q

tendons are derived form what portion of the mesoderm

A

lateral plate mesoderm

somatic region

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4
Q

during the fourth week

A

both limb buds appear
upper - 24 days
lower - 28 days

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5
Q

during the fifth week, limb development

A

has reached hand/foot plate development

chondrificaiton occurs

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6
Q

during the sixth week, limb development has reached the stage of

A

digital rays of hands

limb skeleton is cartilaginous

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7
Q

during the seventh week, limb development has reached the stage of

A

digital rays of feet have formed
osteogenesis begins
limbs begin to rotate

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8
Q

during the 8th week the limb begins to

A

form separate digits using BMP signaling (induces cell apoptosis)

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9
Q

by the 12th week of development, the limbs are undergoing

A

primary ossification

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10
Q

Fgf10 from mesenchyme is responsible for what signaling

A

activates WNT
WNT induces other Fgfs
sets up positive feedback loop FGF–> WNT–>FGF–>WNT
sets up primary gradient

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11
Q

Apical ectodermal ridge controls which axis

A

proximal/distal axis
AER responsible for continued outgrowth
secretes Fgf8

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12
Q

Fgf8 is primarily secreted by

A

the Apical ectodermal ridge (AER)

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13
Q

Fgf8 is a key regulator of _______ and interacts with ______

A

key regulator of distal outgrowth

interacts with Fgf10

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14
Q

hox gene expression pattern correlates with

A

identity elements along proximal distal axis
9-10 –> styolopod
11 –> zeugopod
12-13 –> autopod

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15
Q

Zone of polarizing activity controls what axis development

A

controls AP axis

induced by Shh activity

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16
Q

Shh is associated with the ______ to designate which axis

A
zone of polarizing activity 
AP axis (pinky vs thumb)
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17
Q

paralog

A

gene related to each other due to descent from a common ancestral DNA sequence (commonly duplication)

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18
Q

AP axis specification occurs even before

A

limb bud outgrowth

19
Q

grafting Shh onto the anterior portion of a growing limb bud will result in

A

mirrored medial digits (more pinkies)

20
Q

primary molecular regulator of dorsal/ventral axis

A

Wnt7a controlled by Lmx1b

21
Q

Wnt7a activity is associated with which surface of distal limb

A

Wnt7a does dorsalization

22
Q

BMP controls what process of limb development

A

formation of digits through apoptosis

23
Q

dorsal mass forms ______ and _____ of upper limb but forms the ________ and _______ of lower limb

A

dorsal
extensors and supinators of upper
extensors and abductors of lower

24
Q

ventral mass forms ______ and ______ of upper limb but forms the _______ and _______ of lower limb

A

ventral
flexors and pronators of upper limb
flexors and adductors of lower limb

25
limb rotation occurs as a result of
torsion in femoral/humeral diaphysis
26
upper extremity rotates _________, making the flexor compartment face _____ and extensors ______
upper extremity rotates 90 laterally, flexor compartment faces anteriorly and extensors are posterior
27
lower extremity rotates _________, making the flexors face ______ and the extensors face ______
lower extremity rotates 90 medially, flexors are posterior and extensors are anterior
28
limb rotation begins at week
7
29
sensory axons follow what structure to innervate the muscles
sensory axons follow the efferent axons from the ventral rami innervating the limb muscles
30
limb musculature is derived from
dorsolateral cells of the somites
31
Lmx1b turns on
Wnt7a
32
sorting of innervation, cranial and caudal
axons cranial to limb innervate dorsal musculature | axons caudal to limb innervate ventrocaudal musculature
33
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
34
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
35
late/partial loss of FGF signaling results in
meromelia | absence of part of a limb
36
early loss of FGF signaling results in
amelia | total absence of entire limb
37
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
38
adactyly is a total
absence of digits
39
cutaneous syndactyly
simple webbing of digits .
40
osseous syndactyly
fusion of bones, digital rays fail to develop | BMP disruption or HoxD13 mutation
41
Thalidomide exposure resulted in this melia
phacomelia - absence of long bones with rudimentary hands and feet partial loss of FGF siglaning or Hox disruption
42
FGF8 signaling defects would result in
ectrodactyly/lobster claw deformity - split hand/foot anomaly
43
amnion adhering to fetal structures results in
deletion of those structures | amniotic bands?
44
Bilateral talipes equinovarus
club foot | results from oligohydramnios (deficiency of amniotic fluid) reducing fetal movements