090914 dev of limb

Question 1

limb precursor tissues

Answer 1

limb mesenchyme (somatic mesoderm, somitic mesoderm which is from the somite and forms the abaxial compartment)

surface ectoderm

Question 2

limb development times differ btwn upper and lower limb by

Answer 2

upper limb is ahead of lower limb by 1-2 days

Question 3

when does establishment of the limb field occur?

Answer 3

week 4

Question 4

budding is an inherent property of

Answer 4

mesoderm-the somatic mesoderm

Question 5

apical ectodermal ridge

Answer 5

ectoderm thickening at dorsal and ventral interface

Question 6

what occurs during wks 5-9 w/ regards to limb development

Answer 6

elongation of the limb

tissue formation and organization

Question 7

what does elongation result from?

Answer 7

epithelial-mesenchymal interactions at the AER and mesoderm interface

Question 8

differentiation occurs in what direction

Answer 8

proximal to distal

Question 9

time wise, how does limb development occur in each of the three axes?

Answer 9

simultaneous along all three

Question 10

how does development along the proximal distal axis occur

Answer 10

ectoderm and mesoderm reciprocally signal to each other (Fgf 10, Fgf 8)

proximally, there’s more retinoic acid and distally, there’s more Fgf and Wnt (molecule gradients)

Question 11

roles of the mesenchyme

Answer 11

induces and sustains AER

determines whether it’s upper or lower limb

Question 12

roles of AER

Answer 12

maintains proliferating pool of mesenchyme with Fgf8

maintains ZPA

interacts with proximal-distal and anterior-posterior specific proteins to give mesenchymal cells positional information

Question 13

if you remove the AER what happens

Answer 13

elongation stops; limb is truncated

Question 14

amelia

Answer 14

no limb

Question 15

meromelia

Answer 15

partial limb

Question 16

congenital constrictive band syndrome

Answer 16

when amniotic bands tighten around body parts

Question 17

failure of formation of parts in the transverse direction

Answer 17

amputation along the proximal distal axis

a failure of communication btwn AER and mesoderm

Question 18

what controls anterior posterior patterning

Answer 18

zone of polarizing activity (ZPA), which is at the posterior border of the limb

sonic hedgehog (shh)- (retinoic acid also has the same effect). if provide retinoic acid bead, you get more digits forming along A-P axis

gradient of Shh causes Hox gene combinatorial expression

Question 19

failure of formation of parts in lognitudinal direction

Answer 19

amputation along A-P axis

Question 20

phocomelia

Answer 20

shortened limbs-along A-P axis

Question 21

seal hands

Answer 21

phocomelia

linked often to thalidomide drug exposure

Question 22

what role does apoptosis play in limb development

Answer 22

separation of digits
absence of distal phalanx of large digit

the apoptosis is caused by disappeared of the AER

Question 23

syndactyly

Answer 23

when digits are fused due to failure of separation

Question 24

sirenomelia

Answer 24

legs are fused together developmentally

Question 25

development along the dorsal ventral axis influences what?

Answer 25

skeletal muscles (myoblasts organize into dorsal and ventral premuscle masses)

neural and vascular structures

limb compartmentalization

Question 26

mediators of dorsal ventral patterning

Answer 26

factors like Wnt 7a

transcription factor En

Question 27

sprengel deformity

Answer 27

scapula descended in devleopment when it shouldn’t have

Question 28

cleidocranial dysplasia

Answer 28

abnormal development of limb girdles

missing clavicle

Question 29

talipes equinovarus

Answer 29

turned in hindfoot
adduction of forefoot
plantar flexion of foot
significant crease in instep

unknown what causes it

Question 30

what is the critical period for limb development

Answer 30

wk 4-9

Question 31

somatic mesoderm gives rise to

Answer 31

dermis and connective tissue