Development of the Appendicular Skeleton and Limb Formation

Question 1

When do Limb buds appear?

Answer 1

By the end of the 4rth week.

Question 2

When are limbs fully formed?

Answer 2

By the end of the 8th week.

Question 3

At what week can we see the hand and foot plate, the digital rays in the hand plate and the distal constriciton?

Answer 3

By the 6th week.

Question 4

When do the limbs rotate in opposite directions?

Answer 4

At the 7th week

Question 5

The baby of a pregnant women who ingests thalidomide could have…

Answer 5

Meroamelia

Partial abscence of the limbs.

Question 6

Which is the most common muscoskeletal defect?

Answer 6

Clubfeet

Question 7

From what layers are limbs made of?

Answer 7

Of mesenchyme (parietal layer of lateral mesoderm) and a layer of ectoderm.

Question 8

What part of the limb induces its outgrowth?

Answer 8

The Apical Ectodermal Ridge
(AER)

Question 9

What pattern does the differenciation of the limbs follow?

Answer 9

Follows a proximal-distal differentiation.

Question 10

Which genes are in charge of the regional patterning of the limb?

Answer 10

The HOX genes.

Question 11

When does the mesenchymal bone models undergo chondrification to form hyaline cartilage bone models?

Answer 11

At the 6th week.

Question 12

When do primary ossification centers begin to form in LONG bones?

Answer 12

At the 8th week.

Question 13

When are primary ossification centers present in ALL bones?

Answer 13

At the 12th week.

Question 14

Where is the mutation that causes Achondroplasia?

Answer 14

In the receptor for the Fibroblast Growth Factor 3.