embryo

Question 1

what determines the course of limb development and controls future development of limb?

Answer 1

AER due to presence of fibroblast growth factor

Question 2

what promotes the patterning of distal ends into flat paddle hands/feet

Answer 2

HOX gene

Question 3

when do hand vs feet paddles have 5 digital rays

Answer 3

6th week-hand, 7th week foot

Question 4

when does apoptosis occur of the mesenchymal tissue between digital rays

Answer 4

8th week

Question 5

when do limb buds start to appear/aka activation of mesenchymal cells? specfically upper limb vs lower limb-include which vertebral region?

Answer 5

4th week

upper limb (C5-T1): 26-27 days 
lower limb (L2-S2): 2 days after

Question 6

when does the cartilage model begin? what is it derived from?

Answer 6

5th week; mesenchymal cells

Question 7

when is the entire cartilaginous skeleton complete?

Answer 7

6th week

Question 8

when does endochondrial ossification begins? process? (ie whats the primary ossification center)

Answer 8

7th week; chondrocytes replaced by bone bone producing cells

begins in diaphysis of long bones(primary ossification center)

Question 9

where do myogenic cells originate from? process?

Answer 9

dermomyotome region of somites. then it migrates into mesenchymal cells of limb buds where they differentiate into myoblasts and develop muscle cells of limb

Question 10

what do somites differentiate into?

Answer 10

1. dermatome–stay deep to ectoderm to give rise to skin
2. . myotome
3. sclerotome: axon process of spinal cord

Question 11

upper and lower limb rotation direction, what does the lower limb rotate around

Answer 11

lower limb: 90 deg medial

upper limb: lateral
opposite direction

LL rotate around the profunda femoris

Question 12

extra digits resulting from what? name?

Answer 12

polydactyly: extra digital rays

Question 13

what is syndactyly

Answer 13

attached digits; malformation of apoptosis

Question 14

amelia

Answer 14

absence of limbs

Question 15

meromelia

Answer 15

absence of part of a limb

Question 16

lobster claw deformity is also known as what? cause?

Answer 16

cleft foot/hand result from failure of development of one or more digital rays

appears to be split down in middle

Question 17

brachy dactyly

Answer 17

short digits

Question 18

what is the defect on club foot? how does this affect their gait, what is this also know as

Answer 18

abnormality involving talus

individual walk on ankle rather than foot

sole of foot is turned medially and inverted

Talipes equinovarus

Question 19

what is the role of AER

Answer 19

promote outgrowth and lengthening of limb buds

Question 20

what does mesenchyme form? in the influence of what?

Answer 20

bone, cartilage, blood vessels , joints, fascial layers, lymphatic vessels

in the influence of HOX genes

Question 21

critical period for embryo

Answer 21

24-36 days

Question 22

what does bone form from

Answer 22

mesenchyme

Question 23

where does the core of mesenchymal cesll derive from

Answer 23

somatic component of lateral mesoderm layer of embryo

Question 24

what is the role of HOX gene

Answer 24

control direct cell division and differentiation

Question 25

what causes expression of fibroblast growth factor

Answer 25

inductive influence of AER

Question 26

where are schwann cells derived from

Answer 26

neural crest cells

Question 27

what are the preaxial compartments vs postaxial compartment

Answer 27

preaxial: flexor
postaxial: extensor

Question 28

what drug produces limb defects? when is the most susceptible time for producing limb defect?

Answer 28

thalidomide

days 24-36

Question 29

Talipes equinovarus

Answer 29

congenital club foot: defect involving talus. Walk on ankle rather foot

foot is turned medially and foot inverted