Limb Development

Question 1

In what week to limbs develop? Which set of limbs develop first?

Answer 1

Limb buds form in week 3.

Upper limbs first then lower limbs.

Question 2

When do digits form?

Answer 2

Week 8

Question 3

Initial ossification of limbs begins in what week?

Answer 3

Week 12

Question 4

At week 4, limb-forming mesoderm releases?

Answer 4

FGF 10 (fetal growth factor)

Question 5

What occurs after FGF10 is released?

Answer 5

FGF10 stimulates surface ectoderm to become APICAL ECTODERMAL RIDGE (thickening of surface ectoderm)

Question 6

Once formed, the apical ectodermal ridge releases? What does this stimulate?

Answer 6

FGF 8 and FGF 4, which stimulates the mesoderm

Question 7

What direction does stimulated mesoderm (FGF 8 and 4) grow?

Answer 7

Proximal to Distal

Question 8

Skeletal muscle come from what embryonic layer?

Answer 8

The hypomere of the soMITE mesoderm of the paraxial myotome

Question 9

Cartilage and connective tissue come from what embryonic layer?

Answer 9

the lateral plate of the Somatic mesoderm

Question 10

The stylopod gives rise to what bones?

Answer 10

Humerus and femur

Question 11

The Zeugopod gives rise to what bones?

Answer 11

Radius/Ulna and Tibia/Fibula

Question 12

The Autopod gives rise to what bones?

Answer 12

Carpels, metacapals, digits and tarsals, metatarsals and digits

Question 13

What are the regions of the limbud (proximal to distal)?

Answer 13

SZA
Stylopod
Zeugopod
Autopod

Question 14

What occurs in week 5 of limb development?

Answer 14

Hand Plates form (then foot plates)

Question 15

What occurs in week 6 of limb development?

Answer 15

Digital rays of HAND form from mesenchymal tissue (whole limb is cartilage)

Question 16

What occurs during week 7 of limb development?

Answer 16

Digital rays of FEET
Osteogenesis of long bones
Rotation of Limbs (think of the number 7)

Question 17

What occurs during week 8 of limb development?

Answer 17

Separate digits form through apoptosis of surrounding tissues

Question 18

What causes digits to form in week 8?

Answer 18

BMP which causes apoptosis

Question 19

The peripheral axons are mylinated by?

Answer 19

Schwann Cells (from Neural crest cells)

Question 20

Limb musculature is derived from what?

Answer 20

dorsolateral cells of the somites of the lateral plate mesoderm

Question 21

Sensory axons come from what?

Answer 21

Neural crest cells

Question 22

Sensory axons (neural crest cells) follow ____ and use them for guidance

Answer 22

motor axons (from neural tube/neuroectoderm)

Question 23

Limb rotation occurs during which week?

Answer 23

Week 7!

Question 24

Upper limb rotates _____ 90 degrees while lower limb rotates _____ 90 degrees.

Answer 24

Upper limb rotates laterally

Lower limb rotates medially

Question 25

The brachial artery is derived from what primary arterial structure?

Answer 25

Primary axial artery

Question 26

The primary axial artery eventually becomes what artery?

Answer 26

The brachial artery of the upper limb

Question 27

Talipes Equinovarus

Answer 27

Club Foot | 2x more common in males

Question 28

What is the most common musculoskeletal defect?

Answer 28

Club foot (Talipes Equinovarus)

Question 29

Hip dysplasia is more common in (males/females)

Answer 29

More common in females

Question 30

Oligohydramnios

Answer 30

deficiency in amniotic fluid levels | can cause Club foot (unable to fully rotate)

Question 31

Patterning is regulated by:

Answer 31

HOX genes

Question 32

AER

Answer 32

Apical ectodermal ridge (progress zone of proliferating mesenchyme)

Question 33

what regulates the types and shapes of bones?

Answer 33

HOX genes (patterning)

Question 34

Development of the ventral surface is maintained by

Answer 34

BMPS

Question 35

Development of the dorsal surface is stimulated by

Answer 35

Wnt7

Question 36

___ and ___ collectively set up the apical ectodermal ridge

Answer 36

BMPS and Wnt7

Question 37

Enterior-posterior patterning is established by the _____

Answer 37

Zone of polarizing Activity (ZPA)