Limb Development

Question 1

musculature is derived from what portion of the mesoderm

Answer 1

paraxial mesoderm –> myotome

Question 2

bones are derived from what portion of the mesoderm

Answer 2

lateral plate mesoderm - somatic region

Question 3

tendons are derived form what portion of the mesoderm

Answer 3

lateral plate mesoderm

somatic region

Question 4

during the fourth week

Answer 4

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

Question 5

during the fifth week, limb development

Answer 5

has reached hand/foot plate development

chondrificaiton occurs

Question 6

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

Answer 6

digital rays of hands

limb skeleton is cartilaginous

Question 7

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

Answer 7

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

Question 8

during the 8th week the limb begins to

Answer 8

form separate digits using BMP signaling (induces cell apoptosis)

Question 9

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

Answer 9

primary ossification

Question 10

Fgf10 from mesenchyme is responsible for what signaling

Answer 10

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

Question 11

Apical ectodermal ridge controls which axis

Answer 11

proximal/distal axis
AER responsible for continued outgrowth
secretes Fgf8

Question 12

Fgf8 is primarily secreted by

Answer 12

the Apical ectodermal ridge (AER)

Question 13

Fgf8 is a key regulator of _______ and interacts with ______

Answer 13

key regulator of distal outgrowth

interacts with Fgf10

Question 14

hox gene expression pattern correlates with

Answer 14

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

Question 15

Zone of polarizing activity controls what axis development

Answer 15

controls AP axis

induced by Shh activity

Question 16

Shh is associated with the ______ to designate which axis

Answer 16

zone of polarizing activity 
AP axis (pinky vs thumb)

Question 17

paralog

Answer 17

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

Question 18

AP axis specification occurs even before

Answer 18

limb bud outgrowth

Question 19

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

Answer 19

mirrored medial digits (more pinkies)

Question 20

primary molecular regulator of dorsal/ventral axis

Answer 20

Wnt7a controlled by Lmx1b

Question 21

Wnt7a activity is associated with which surface of distal limb

Answer 21

Wnt7a does dorsalization

Question 22

BMP controls what process of limb development

Answer 22

formation of digits through apoptosis

Question 23

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

Answer 23

dorsal
extensors and supinators of upper
extensors and abductors of lower

Question 24

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

Answer 24

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

Question 25

limb rotation occurs as a result of

Answer 25

torsion in femoral/humeral diaphysis

Question 26

upper extremity rotates _________, making the flexor compartment face _____ and extensors ______

Answer 26

upper extremity rotates 90 laterally, flexor compartment faces anteriorly and extensors are posterior

Question 27

lower extremity rotates _________, making the flexors face ______ and the extensors face ______

Answer 27

lower extremity rotates 90 medially, flexors are posterior and extensors are anterior

Question 28

limb rotation begins at week

Answer 28

7

Question 29

sensory axons follow what structure to innervate the muscles

Answer 29

sensory axons follow the efferent axons from the ventral rami innervating the limb muscles

Question 30

limb musculature is derived from

Answer 30

dorsolateral cells of the somites

Question 31

Lmx1b turns on

Answer 31

Wnt7a

Question 32

sorting of innervation, cranial and caudal

Answer 32

axons cranial to limb innervate dorsal musculature

axons caudal to limb innervate ventrocaudal musculature

Question 33

axial arteries in upper and lower limb develop _________ at __ and __ days post fert, respectively

Answer 33

develop de novo
30 days in upper
36 dpf in lower

Question 34

vasculature for limbs involves remodeling of what structures

Answer 34

7th cervical intersegmental a
5th lumbar intersegmental a
Originate within surrounding mesoderm and join dorsal aorta - branch to join axial artery

Question 35

late/partial loss of FGF signaling results in

Answer 35

meromelia

absence of part of a limb

Question 36

early loss of FGF signaling results in

Answer 36

amelia

total absence of entire limb

Question 37

overexpression of Shh can result in

Answer 37

polydactyly - presence of supernumerary digits
forms second ZPA
extra digit lacks normal musculature
usually most medial/lateral digit is duplicated

Question 38

adactyly is a total

Answer 38

absence of digits

Question 39

cutaneous syndactyly

Answer 39

simple webbing of digits .

Question 40

osseous syndactyly

Answer 40

fusion of bones, digital rays fail to develop

BMP disruption or HoxD13 mutation

Question 41

Thalidomide exposure resulted in this melia

Answer 41

phacomelia - absence of long bones with rudimentary hands and feet
partial loss of FGF siglaning or Hox disruption

Question 42

FGF8 signaling defects would result in

Answer 42

ectrodactyly/lobster claw deformity - split hand/foot anomaly

Question 43

amnion adhering to fetal structures results in

Answer 43

deletion of those structures

amniotic bands?

Question 44

Bilateral talipes equinovarus

Answer 44

club foot

results from oligohydramnios (deficiency of amniotic fluid) reducing fetal movements