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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
What causes deformation
Contraction bands
26
What causes malformation
Intrinsic error (e.g. Wrong signalling due to mutation) in coordinating morphogenesis
27
Why does the AER regress
To ensure separation of the digits
28
What appear in the final stages growth from the AER
Paddles
29
Which cells do the AER exert an effect on
The immediately underlying mesenchymal cells
30
Why does the proximal mesenchymal cells to the AER begin to differentiate
They are too far away from the AER so don't have the AER's influence
31
What process progressively sculpts the interdigital spaces
Apoptosis
32
What happens to the limbs before they rotate
Extend ventrally
33
Which spinal segments does the upper limb appear opposite to
Caudal cervical spinal segments
34
What spinal segments does the lower limb appear opposite to
Lumbar and sacral spinal segments
35
What type of tissue migrates to the limbs from the somites
Myogenic (precursor to muscle)
36
What happens to the myogenic tissue as it enters the limb bud
Splits into 2 muscle masses around the newly forming skeletal structures
37
What are the names of the 2 muscle masses formed in the limb bud when the myogenic muscle migrates into the limb bud
Ventral (flexor) and dorsal (extensor) compartments
38
what will the sclerotome develop into
vertebrae and ribs
39
what will the dermatomyotome separate into
dermatome and myotome
40
what type of nerve fibres do the dorsal roots contain
afferent / sensory fibres
41
what type of nerve fibres do the ventral roots contain
efferent / motor and autonomic fibres
42
what is true about the nerve supply to skin and muscle derived from a single dermatomyotome
they have a common spinal nerve supply
43
what type of neurones are found in the spinal cord
a mix of sensory and motor neurones
44
where do the spinal nerves pass out of
the intervertebral foramina
45
how many pairs of spinal nerves are there
31
46
what does the spinal cord run down
the vertebral foramen
47
what is the spinal canal
multiple vertebral foramina
48
what do the vertebral segments differentiate from
sclerotomes
49
where does the spinal cord start and end
starts at the inferior margin of the medulla oblongata and ends as the conus medullaris at L2
50
true or false: most spinal cord segments are vertically aligned with their corresponding vertebrae
false
51
where do long roots from the inferior segments to L2 descend into
cauda equina
52
which pairs of spinal nerves emerge above their corresponding vertebrae
C1-C7
53
where does the spinal nerve C8 exit from
above the T1 vertebra but below the C7 vertebra
54
where do the spinal nerves T1-L5 exit
below their corresponding vertebra
55
what are rami
divisions of the spinal cord after it exits through the intervertebral foramina
56
what are the 2 rami that the spinal nerve divides into
posterior and anterior rami
57
what does the posterior rami divide into
medial and lateral branches
58
where does the posterior rami innervate
deep muscles and skin of the back
59
where does the anterior rami innervate
muscles and skin of the front, upper limbs and lower limbs
60
what are meningeal branches
branches of spinal nerve that re-enter the spinal canal through the intervertebral foramen to supply the vertebrae, ligaments, blood vessels and meninges
61
what are rami communicantes
components of the ANS
62
true of false: the segments of muscle and skin supplied by the dorsal rami are in line with the intervertebral foramina
true
63
true of false: the segments of muscle and skin supplied by the anterior rami are in line with the intervertebral foramina
false
64
as the dermatomyotome spreads out what happens to the spinal nerve supplying it
it spreads out too
65
what is a myotome
a group of muscles supplied by a single spinal nerve
66
what Is a dermatome
area of skin supplied by a single spinal nerve
67
what is a motor unit
a motor neurone and the skeletal muscle fibres it innervates
68
what is an axial line
junction of 2 dermatomes supplied from discontinuous spinal levels
69
what do axial line mark
the centre of either the ventral or dorsal compartments of the limb
70
what marks the pre-axial and post-axial boundaries
veins
71
what veins mark the pre and post axial boundaries in the arm
``` pre = cephalic post = basilic ```
72
what veins mark the pre and post axial boundaries in the lower limb
``` pre = long saphenous post = short saphenous ```
73
true or false: within a peripheral nerve territory there may be fibres from more than 1 spinal nerve
true
74
true or false: fibres from one spinal nerve can only enter 1 peripheral nerve territory
false
75
what is herpes zoster
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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