embryology

Question 1

limb buds appear in

Answer 1

4th week

Question 2

limb buds derived from

Answer 2

mesoderm,ectoderm and parietal layer of lateral mesoderm

Question 3

ectoderm proliferates into

Answer 3

Apical Ectodermal Ridge (AER)

Question 4

what does AER do

Answer 4

stimulates the mesenchyme to be a population of undifferentiated rapidly proliferting cells called the prgress zone.

Question 5

development of the limb proceeds in what direction

Answer 5

proximodistally

Question 6

6th week

Answer 6

hand and foot plates formed

Question 7

fingers and toes are formed how?

Answer 7

by cell death of the ridge into 5 parts

Question 8

development of upper limb is faster than lower limb by

Answer 8

1 to 2 days

Question 9

7th week

Answer 9

limbs rotate in different directions

Question 10

upper limb rotates

Answer 10

90° laterally. extensor muscles lie laterally and posterioly and thumbs lie on the lateral side.

Question 11

lower limb rotates

Answer 11

90° medially extensor muscles lie medially and big toe is medial.

Question 12

6th week again

Answer 12

first hyaline cartilage models form

Question 13

12th week

Answer 13

primary ossification centers are present in all long bones .