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Year 3 - Musculoskeletal > Development of limbs > Flashcards

Development of limbs Flashcards

1
Q

When does limb development being?

A

Near the end of the 4th week

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2
Q

What leads to activation of limb development?

A

Activation of mesenchymal cells int he somatic lateral mesoderm

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3
Q

What regulates patterning within limb development?

A

Homeobox genes regulate patterning

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4
Q

Which day do the upper Limb buds appear?

A

Day 24

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5
Q

When do the lower limb buds appear?

A

Day 25-26

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6
Q

What are HOX genes?

A

Regionally expressed in limbs and determine which skeletal element formed
HOX gene expression results from a combination of the
expression of SHH (Sonic Hedgehog), FGF’s (Fibroblast Growth Factors) and WNT-7a

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7
Q

Which HOX genes are expressed in upper limb?

A

HOXd 9-13

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8
Q

If you removed HOX 11 and HOXd 11 what would occur?

A

Radius and ulna would not form

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9
Q

HOX 9?

A 
> Scapula*
> Humerus 
> Radius and ulna 
> Carpals 
> Metacarals and > phalanges
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10
Q

HOX 10?

A

> Humerus*
Radius and ulna
Carpals
Metacarals and > phalanges

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11
Q

HOX 11?

A

> Radius and ulna*
Carpals
Metacarals and > phalanges

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12
Q

HOX 12?

A

> Carpals*

> Metacarals and > phalanges

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13
Q

HOX 13?

A

> Metacarals and phalanges*

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14
Q

How do limb buds occur?

A

Elongate by the proliferation of mesenchyme

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15
Q

Upper limb buds develop opposite what?

A

Caudal cervical segments

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16
Q

Lower limb buds develop opposite what?

A

The lumbar and sacral segments

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17
Q

At the apex of limb bud the ectoderm thickens to form what?

A

Apical ectodermal ridge (AER)

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18
Q

Where is the apical ectodermal ridge restricted to?

A

End of limb bud

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19
Q

The mesenchyme adjacent to the AER consits of what?

A

Undifferentiated, rapidly proliferating cells

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20
Q

whereas mesenchymal cells proximal to it differentiate into what?

A

Blood vessels and cartilage bone models

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21
Q

What is the apical ectodermal ridge?

A

> Thickened section of the ectoderm consisting of a multinucleate epithelial structure

> Exerts an inductive influence on the limb mesenchyme

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22
Q

What occurs day 32 of development - limb development?

A

Paddle-like-upper limb bud

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23
Q

What occurs day 35 of development - limb development?

A

Handplate formed

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24
Q

What occurs day 44 (Week 6) of development - limb development?

A

> Digital rays appear in hand plate
Notch between digital rays, webbed fingers

> Lower limb bud

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25
Q

What occurs day 48 (Week 7) of development - limb development?

A

> Upper limbs bend at the elbow
Fingers are slightly short and webbed

> Digital rays are formed in the foot plate

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26
Q

What occurs day 58 (Week 8) of development - limb development?

A

Fingers and toes are distinct and separated

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27
Q

Why is apoptosis important within limb development?

A

Programmed cell death (apoptosis) is responsible for the tissue breakdown in the
interdigital regions –mediated by bone morphogenetic proteins

28
Q

How are cartilaginous precursors of limb nones developed, when?

A

Chondrification and by week 6

29
Q

When do primary centres of ossification appear?

A

Between weeks 8 and 12 of development

30
Q

Which type of ossification occurs during limb development?

A

Endochondrial ossification for all limb bones except the clavicle (membranous)

31
Q

Which type of ossification occurs during development of the clavicle?

A

Membranous ossification

32
Q

What has to happen for the upper limbs to be positioned correctly?

A

Upper limbs rotate 90o laterally so that extensors are on the lateral and posterior surfaces (and the thumb is lateral)

33
Q

What has to happen for the lower limbs to be positioned correctly?

A

Lower limbs rotate 90o medially so that the extensors are on the anterior surface (and the big toe is medial)

34
Q

Which way do upper limbs rotate during development?

A

90o laterally

35
Q

Which way do lower limbs rotate during development?

A

90o medially

36
Q

Which week of development do peripheral nerves grow from developing limb plexus?

A

The 5th week

37
Q

Limb birth defects - Total absence?

A

Amelia

38
Q

Limb birth defects - partial absence?

A

Meromelia

39
Q

Limb birth defects, - some long bone absence?

A

Phocomelia

40
Q

Limb birth defects - all parts present but small?

A

Micromelia

41
Q

Mode of inheritance of lobster claw foot?

A

Autosomal dominated trait

42
Q

Critical period of limb development?

A

14-26 days after fertilisation

43
Q

What is polydactyly?

A

Presence of more than 5 digits on the hands or feet

44
Q

Cause of polydactyly?

A

Can be either teratogen induced or inherited

45
Q

Characteristics of extra digit in polydactyly?

A

Extra digit is incompletely formed and lacks muscular development

46
Q

What is cutaneous syndactyly?

A 
Cutaneous Syndactyly (simple webbing between the digits) is
a common limb defect
47
Q

What is osseous syndactyly?

A

Osseous Syndactyly (fusion of bones) occurs when notches between the digital rays fail to develop

48
Q

Does syndactyly occur more frequently in the hand or the foot?

A

The foot

49
Q

Syndactyly, common or rare?

A

Common birth defect in the hand or foot

50
Q

What is thalidomide?

A

> Used between 1957-1962 was a commonly used sleeping tablet and anti-nauseant

> Now used to help cancer, leprosy and AIDs patients

51
Q

When should thalidomide not be taken?

A

> During pregnancy particularly within the sensitive period, weeks 4-8

> For this reason we do not give it to woman of child bearing age

52
Q

How can thalidomide effect development?

A

> Absence or deformity of long bones
Intestinal atresia
Cardiac anomalies

53
Q

What is the name for clubfoot?

A

Talipes equinovarus

54
Q

What is Talipes equinovarus (club foot)?

A

The sole of the foot is turned medially and the foot is inverted?

55
Q

What is cause of Talipes equinovarus (club foot)?

A

1) Multifactoral (Genetic and environment factors)

2) Abnormal positioning or restricted movement of the foetus’s lower limb in utero - Evidence is inconclusive

56
Q

Which percentage of infants have congenital dislocation of the hip?

A

15% of infants

57
Q

When does congenital dislocation of the hip usually occur?

A

Common after breeched deliveries

58
Q

What causes developmental dysplasia of the hip?

A

Abnormal development of acetabulum

59
Q

Generalised joint laxity?

A

> Multifactorial

> Associated with congenital dislocation of the hip

60
Q

Could label the diagram above and ask to identify the apical ectodermal ridge

A

Slide 4 of lectures embryology

61
Q

What is the last step in the development of hands and feet?

A

Loss of the webs separating the digits of finger and toes

62
Q

The process of bone formation is known as what?

A

Ossification

63
Q

Epiphyseal cartilage form what?

A

The growth plates

64
Q

Cartilage to bone is known as what?

A

Endochondrial ossification

65
Q

Myofilaments form from what?

A

Mesochyme tissue = Myoblasts and myotubes

Some are from neurocrest cells

66
Q

Syndactyly an come up in exam to identify

A

E.g. Radiograph shows osssous syndactyl

67
Q

What are Homebox (HOX) genes mainly involved in?

A

Limb development

Year 3 - Musculoskeletal (30 decks)

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