Lecture 19: Limb Development Flashcards Preview

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Flashcards in Lecture 19: Limb Development Deck (61)
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1

Which develops first? Lower limbs or upper limbs?

Upper Limbs develop first

2

In what week do the upper and lower limbs begin to develop?

Week 4

3

Why do the upper limbs develop slightly ahead?

Better blood supply due to the fact that the embryo favors supplying the brain - and therefore the upper half of the embryo - with blood.

4

When do the limb buds develop?

4th Week

5

What embryological structure gives rise to the muscle of the limbs?

The Hypomere (Pariaxial Mesoderm -> Somite -> Myotome -> Hypomere)

6

Where does the cartilage and connective tissue of the upper limb come from embryologically?

 

What does cartilage serve as a precursor for in the upper limb?

Somatic Lateral Plate Mesoderm

 

Bone

7

Where do the Fascia and Blood Vessels of the upper extremity come from?

Somatic Lateral Plate Mesoderm

(They are part of the Connective Tissue)

8

What is the "Limb Forming Mesoderm" made of?

Pariaxial and Somatic Lateral Plate Mesoderm

9

What stimulates the Surface Ectoderm to become the Apical Ectodermal Ridge?

FGF 10

10

What is the Apical Ectodermal Ridge made of?

Surface Ectoderm

The Apical Ectodermal Ridge is just a thickening of the surface ectoderm that was already there in response to FGF 10

11

What releases FGF 10?

The Limb - Forming Mesoderm

12

What releases FGF 4 and 8?

The Apical Ectodermal Ridge

13

What do FGF 4 and 8 do?

Stimulate growth of the Limb-Bud Mesoderm

14

What "fates" certain regions of the Limb-Forming Mesoderm to become certain bones?

Concentration gradients of signaling molecules.

15

What does the Stylopod give rise to?

Humerus and Femur

16

What does the Zeugopod give rise to?

Ulna/Radius

Tibia/Fibula

17

What does the Autopod give rise to?

Carpals/Metacarpals and Digits of the Hand

Tarsals/Metatarsals and Digits of the Foot

18

When do the Hand and Foot Plates Develop?

Week 5?

19

When do the Digital Rays of the Hand develop?

Week 6

20

When do the Digital Rays of the Feet develop?

Week 7

21

When do the limbs rotate?

Week 7

22

When do the long bones begin to ossify?

Week 7

23

When do we start to separate our digits?

Week 8

24

What pro-apoptotic family is responsible for separating our digits?

 

If these are down-regulated, what conditions might we see?

BMP's

 

Webbed fingers or Syndactyly

25

When do Chondrification Centers appear?

Week 5

26

During Week 6, what is the status of the limb skeleton?

The entire limb skeleton is cartilage during Week 6.

27

In what region of the embryo is the limb bud forming?

The Cervical Region

28

In what region is the leg bud forming?

The Lumbosacral Region

 

29

When do Motor Axons from the spinal cord enter the limb buds?

Week 5

30

What gives rise to motor neurons?

Neural Tube (Neuroectoderm)