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Musculoskeletal System > Embryology > Flashcards

Embryology Flashcards

1
Q

When do limb buds begin to develop

A

End of the 4th week

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2
Q

What type of cells are limb buds made up of

A

Mesenchymal stem cells with ectoderm covering

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3
Q

True or false; the lower limb development lags behind the development of the upper limb

A

True. It lags behind by 2 days

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4
Q

How does the limb bud elongated

A

Proliferation of mesenchymal cells

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5
Q

What are the 3 axes for asymmetrical limb development

A
  1. Shoulder to fingertips (proximal to distal axis)
  2. Palmar surface to dorsal surface (dorsal to ventral axis)
  3. Side to side (anterior to posterior axis)
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6
Q

What controls the development to anterior - posterior axis asymmetry

A

Cone of polarising activity (ZPA)

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7
Q

What controls the asymmetrical development in the proximal - distal axis

A

Apical ectodermal ridge (AER)

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8
Q

What controls the development of dorsal - ventral development

A

Dorsal Ectoderm

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9
Q

What is syndactyly

A

Fusion of digits, may involve just connective tissue or bones may be fused

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10
Q

What is polydactyly

A

Extra digits

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11
Q

True or false; polydactyly is a genetic dominant trait

A

False; it’s actually recessive

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12
Q

What is Amelia

A

Complete absence of a limb

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13
Q

What is meromelia

A

Partial absence of on or more limbs

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14
Q

What is phocomelia

A

Where the hands and feet are directly attached to the trunk of the body

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15
Q

Which direction does the upper limb rotate in development

A

Laterally (thumb ends up lateral)

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16
Q

What direction does the lower limb rotate during development

A

Medially

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17
Q

Where is the Apical Ectodermal Ridge located

A

Dense region at the apex of the limb bud

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18
Q

What does the AER do?

A

Prevents differentiation of mesenchymal cells in the limb bud. Causes proliferation of these cells to extend the limb in the proximal to distal direction

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19
Q

Where are the cells of the ZPA located

A

Posterior base of the limb bud

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20
Q

True of false; the ZPA also controls patterning and maintenance of the AER

A

True

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21
Q

How do the digits form?

A

Mesenchymal cells of the paddle condense forming notches. Cartilaginous models of the bones then forms. Apoptosis then occurs of the AER to separate the digits.

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22
Q

Give 2 examples of an external agents which causes limb disruption

A

Thalidomide and infections (e.g. Rubella)

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23
Q

What does thalidomide do

A

Disrupts the AER to stop elongation

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24
Q

What are constriction bands

A

When strands come off from mesenchymal tissue to form bands which restrict limb buds cutting part of the limb off

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25
Q

What causes deformation

A

Contraction bands

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26
Q

What causes malformation

A

Intrinsic error (e.g. Wrong signalling due to mutation) in coordinating morphogenesis

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27
Q

Why does the AER regress

A

To ensure separation of the digits

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28
Q

What appear in the final stages growth from the AER

A

Paddles

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29
Q

Which cells do the AER exert an effect on

A

The immediately underlying mesenchymal cells

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30
Q

Why does the proximal mesenchymal cells to the AER begin to differentiate

A

They are too far away from the AER so don’t have the AER’s influence

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31
Q

What process progressively sculpts the interdigital spaces

A

Apoptosis

32
Q

What happens to the limbs before they rotate

A

Extend ventrally

33
Q

Which spinal segments does the upper limb appear opposite to

A

Caudal cervical spinal segments

34
Q

What spinal segments does the lower limb appear opposite to

A

Lumbar and sacral spinal segments

35
Q

What type of tissue migrates to the limbs from the somites

A

Myogenic (precursor to muscle)

36
Q

What happens to the myogenic tissue as it enters the limb bud

A

Splits into 2 muscle masses around the newly forming skeletal structures

37
Q

What are the names of the 2 muscle masses formed in the limb bud when the myogenic muscle migrates into the limb bud

A

Ventral (flexor) and dorsal (extensor) compartments

38
Q

what will the sclerotome develop into

A

vertebrae and ribs

39
Q

what will the dermatomyotome separate into

A

dermatome and myotome

40
Q

what type of nerve fibres do the dorsal roots contain

A

afferent / sensory fibres

41
Q

what type of nerve fibres do the ventral roots contain

A

efferent / motor and autonomic fibres

42
Q

what is true about the nerve supply to skin and muscle derived from a single dermatomyotome

A

they have a common spinal nerve supply

43
Q

what type of neurones are found in the spinal cord

A

a mix of sensory and motor neurones

44
Q

where do the spinal nerves pass out of

A

the intervertebral foramina

45
Q

how many pairs of spinal nerves are there

A

31

46
Q

what does the spinal cord run down

A

the vertebral foramen

47
Q

what is the spinal canal

A

multiple vertebral foramina

48
Q

what do the vertebral segments differentiate from

A

sclerotomes

49
Q

where does the spinal cord start and end

A

starts at the inferior margin of the medulla oblongata and ends as the conus medullaris at L2

50
Q

true or false: most spinal cord segments are vertically aligned with their corresponding vertebrae

A

false

51
Q

where do long roots from the inferior segments to L2 descend into

A

cauda equina

52
Q

which pairs of spinal nerves emerge above their corresponding vertebrae

A

C1-C7

53
Q

where does the spinal nerve C8 exit from

A

above the T1 vertebra but below the C7 vertebra

54
Q

where do the spinal nerves T1-L5 exit

A

below their corresponding vertebra

55
Q

what are rami

A

divisions of the spinal cord after it exits through the intervertebral foramina

56
Q

what are the 2 rami that the spinal nerve divides into

A

posterior and anterior rami

57
Q

what does the posterior rami divide into

A

medial and lateral branches

58
Q

where does the posterior rami innervate

A

deep muscles and skin of the back

59
Q

where does the anterior rami innervate

A

muscles and skin of the front, upper limbs and lower limbs

60
Q

what are meningeal branches

A

branches of spinal nerve that re-enter the spinal canal through the intervertebral foramen to supply the vertebrae, ligaments, blood vessels and meninges

61
Q

what are rami communicantes

A

components of the ANS

62
Q

true of false: the segments of muscle and skin supplied by the dorsal rami are in line with the intervertebral foramina

A

true

63
Q

true of false: the segments of muscle and skin supplied by the anterior rami are in line with the intervertebral foramina

A

false

64
Q

as the dermatomyotome spreads out what happens to the spinal nerve supplying it

A

it spreads out too

65
Q

what is a myotome

A

a group of muscles supplied by a single spinal nerve

66
Q

what Is a dermatome

A

area of skin supplied by a single spinal nerve

67
Q

what is a motor unit

A

a motor neurone and the skeletal muscle fibres it innervates

68
Q

what is an axial line

A

junction of 2 dermatomes supplied from discontinuous spinal levels

69
Q

what do axial line mark

A

the centre of either the ventral or dorsal compartments of the limb

70
Q

what marks the pre-axial and post-axial boundaries

A

veins

71
Q

what veins mark the pre and post axial boundaries in the arm

A 
pre = cephalic 
post = basilic
72
Q

what veins mark the pre and post axial boundaries in the lower limb

A 
pre = long saphenous 
post = short saphenous
73
Q

true or false: within a peripheral nerve territory there may be fibres from more than 1 spinal nerve

A

true

74
Q

true or false: fibres from one spinal nerve can only enter 1 peripheral nerve territory

A

false

75
Q

what is herpes zoster

A

a viral infection affecting a single dermatome. it remains dormant in the dorsal root ganglion until the host is immunosuppressed then it reactivates and travels to a single dermatome

Musculoskeletal System (11 decks)

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