Session 3 - Development of the Limbs Flashcards Preview

Semester 2 - MSK > Session 3 - Development of the Limbs > Flashcards

Flashcards in Session 3 - Development of the Limbs Deck (50):
1

What appears at fourth week of development?

Limb buds

2

What are the limb buds in embryonic development made up of?

Core of proliferating mesenchymal cells with an ectoderm covering

3

What are A and B?

A - Anterior B - Posterior

4

What are C and D?

C - Dorsal D - Ventral

5

What are E and F?

E - Distal F - Proximal

6

Give two examples of a dorsal location on the body

Back of the hand and top of the foot

7

Give two examples of a ventral position on a foetus

Palm of the hand and sole of the foot

8

What is the proximo-distl axis?

Base of the limb to the tips of the digits

9

What is the antero-posterior axis

From 1st digit to 5th

10

Where do limb buds first appear?

On the ventro-lateral body wall

11

What order to limb buds appear in?

Upper limb first, lower limb second

12

In which direction do limb buds at first extend?

Ventrally at first

13

What does limb development begin with?

Activation of mesenchyme within lateral mesoderm

14

Where are limb buds derived from?

The somatic layer of lateral plate mesoderm

15

What does somatic mesoderm contribute to?

Limb skeleton

16

What do somites contribute to?

Musculature

17

What is mesenchyme?

Flexible mesoderm

18

How does limb bud elongate?

Through proliferation of mesenchyme core

19

Give a feature of the apex of a limb bud

Thickened ectoderm

20

Give the three degrees of asymmetry of limb development

Top and bottom (Shoulder to fingertips) Front and back (No hairy palms) Side to side (Left and right hands mirror images)

21

What is the AER?

The apical ectodermal ridge

22

What is the AER critical for?

Limb bud outgrowth

23

What does the AER facillitate?

Limb development, proximal to distal

24

What is the final appearance of the AER before it regressed?

Appearance of paddles

25

What is the arrow pointing to?

The Apical Ectodermal Ridge

26

What are the anatomical effects of the AER?

Causes differentiation of underlying tissue, before finally inducing development of the digits within the hand/foot plates

27

What is the ZPA?

Zone of polarising activity

28

What are the three functions of the zone of polarising activity?

Generation of assymetry in the limbs

Asignalling centra located at the posterior base of the limb bud

Controls both patterning and maintains the AER

29

What does the AER mark the boundary between?

The dorsal and ventral ectoderm

30

Label A, B and C

A - Dorsal ectoderm B - Ventral ectoderm C - AER

31

What does AER mark the boundary between?

32

What do preaxial and postaxial refer to?

Preaxial - Medial - Thumb and Big to

Postaxial - Lateral - Little finger and little toe

33

What controls anterior/posterior development?

ZPA

34

What controls proximal - distal development?

AER

35

What controls dorsal/ventral development?

Ectoderm

36

What occurs in hand and foot plates to convert them from buds to appendages?

Digital rays

Mesenchyme condensations within plates

Cartaliginous models of the digital bone

Apoptosis

Of the tissues between the digits

37

What is syndactyly?

Fusion of digits, may involve just CT or bones may be fused

38

Polydactyly

Extra digits, genetic recessive trait

39

What happens to lateral plate mesoderm?

What is Amelia?

Condenses and diffentiates, undergoes endochondral ossification. 

Amelia - Complete abcense of a limb

40

How do long bones extend?

What is Meromelia?

Secondar ossification centres appear in epiphyses. Bone growth maintained by cartilage forming regions (epiphyseal growth plates)

Partial abcesnse of one or more limb structures

41

How is musculature formed?

Myogenic precursors migratre into limbs from somites. Form two muscles msses - Vental (flexors) and dorsal (extensors)

42

What is the difference in comparments between upper and lower limb?

U limb - flexor anterior

L limb - flexor posterior

43

How do the reveresed compartments formed in upper limbs and legs?

Both limbs extend ventrally

However

  • Upper limb: rotates laterally
  • Lower limb: rotates medially

44

Why do limbs have the innervation they do?

Upper limb bud appears opposite the caudal cervical spinal segments

45

Why is innervation vital to limb development?

Without it development stalls

46

Describe formation of brachial plexus

Anterior divisions for anterior compartments - Regroup to form lateral and medial cords. 

Posterior compartments supplied by posterior divisions 

47

Why do nails have different innervation to rest of dorsal surface of hand?

Nails develop from nail fields on the tips of the fingers

48

What is a dermatome?

A single strip f skin supplied by a single spinal nerve?

49

What is a myotome?

Myotome is a muscle/group of muscles supplied by a single spinal nerve

50

What occurs in hand and foot plates to convert them from buds to appendages?

Digital rays

Mesenchyme condensations within plates

Cartaliginous models of the digital bone

Apoptosis

Of the tissues between the digits