Session 3 - Development of the Limbs Flashcards Preview

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

What appears at fourth week of development?

A

Limb buds

2
Q

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

A

Core of proliferating mesenchymal cells with an ectoderm covering

3
Q

What are A and B?

A

A - Anterior B - Posterior

4
Q

What are C and D?

A

C - Dorsal D - Ventral

5
Q

What are E and F?

A

E - Distal F - Proximal

6
Q

Give two examples of a dorsal location on the body

A

Back of the hand and top of the foot

7
Q

Give two examples of a ventral position on a foetus

A

Palm of the hand and sole of the foot

8
Q

What is the proximo-distl axis?

A

Base of the limb to the tips of the digits

9
Q

What is the antero-posterior axis

A

From 1st digit to 5th

10
Q

Where do limb buds first appear?

A

On the ventro-lateral body wall

11
Q

What order to limb buds appear in?

A

Upper limb first, lower limb second

12
Q

In which direction do limb buds at first extend?

A

Ventrally at first

13
Q

What does limb development begin with?

A

Activation of mesenchyme within lateral mesoderm

14
Q

Where are limb buds derived from?

A

The somatic layer of lateral plate mesoderm

15
Q

What does somatic mesoderm contribute to?

A

Limb skeleton

16
Q

What do somites contribute to?

A

Musculature

17
Q

What is mesenchyme?

A

Flexible mesoderm

18
Q

How does limb bud elongate?

A

Through proliferation of mesenchyme core

19
Q

Give a feature of the apex of a limb bud

A

Thickened ectoderm

20
Q

Give the three degrees of asymmetry of limb development

A

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

21
Q

What is the AER?

A

The apical ectodermal ridge

22
Q

What is the AER critical for?

A

Limb bud outgrowth

23
Q

What does the AER facillitate?

A

Limb development, proximal to distal

24
Q

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

A

Appearance of paddles

25
Q

What is the arrow pointing to?

A

The Apical Ectodermal Ridge

26
Q

What are the anatomical effects of the AER?

A

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

27
Q

What is the ZPA?

A

Zone of polarising activity

28
Q

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

A

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
Q

What does the AER mark the boundary between?

A

The dorsal and ventral ectoderm

30
Q

Label A, B and C

A

A - Dorsal ectoderm B - Ventral ectoderm C - AER

31
Q

What does AER mark the boundary between?

A
32
Q

What do preaxial and postaxial refer to?

A

Preaxial - Medial - Thumb and Big to

Postaxial - Lateral - Little finger and little toe

33
Q

What controls anterior/posterior development?

A

ZPA

34
Q

What controls proximal - distal development?

A

AER

35
Q

What controls dorsal/ventral development?

A

Ectoderm

36
Q

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

A

Digital rays

Mesenchyme condensations within plates

Cartaliginous models of the digital bone

Apoptosis

Of the tissues between the digits

37
Q

What is syndactyly?

A

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

38
Q

Polydactyly

A

Extra digits, genetic recessive trait

39
Q

What happens to lateral plate mesoderm?

What is Amelia?

A

Condenses and diffentiates, undergoes endochondral ossification. 

Amelia - Complete abcense of a limb

40
Q

How do long bones extend?

What is Meromelia?

A

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
Q

How is musculature formed?

A

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

42
Q

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

A

U limb - flexor anterior

L limb - flexor posterior

43
Q

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

A

Both limbs extend ventrally

However

  • Upper limb: rotates laterally
  • Lower limb: rotates medially
44
Q

Why do limbs have the innervation they do?

A

Upper limb bud appears opposite the caudal cervical spinal segments

45
Q

Why is innervation vital to limb development?

A

Without it development stalls

46
Q

Describe formation of brachial plexus

A

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

Posterior compartments supplied by posterior divisions 

47
Q

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

A

Nails develop from nail fields on the tips of the fingers

48
Q

What is a dermatome?

A

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

49
Q

What is a myotome?

A

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

50
Q

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

A

Digital rays

Mesenchyme condensations within plates

Cartaliginous models of the digital bone

Apoptosis

Of the tissues between the digits