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MSK - Final > 10/10 Limb Development - Dennis > Flashcards

10/10 Limb Development - Dennis Flashcards

1
Q

What is musculature derived from?

A

paraxial mesoderm which produces myotomes

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2
Q

What are bones derived from?

A

lateral plate mesoderm from the somatic region

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3
Q

What are tendons derived from?

A

lateral plate mesoderm from the somatic region

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4
Q

At what point point are both limb buds present?

A

4th week

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5
Q

At what point do hand/feet plates appear>

A

5th week

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6
Q

At what point does chondrification begin?

A

5th week

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7
Q

At what point do the digital rays of hands appear?

A

6th week

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8
Q

At what point do we see a cartilaginous limb skeleton?

A

6th week

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9
Q

At what point do the digital rays of the feet appear?

A

7th week

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10
Q

At what point does osteogenesis begin?

A

7th week

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11
Q

At what point does limb rotation begin?

A

7th week

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12
Q

At what point do separate digits form?

A

8th week

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13
Q

At what point does primary ossification begin?

A

12th week

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14
Q

At what point does the upper limb bud form?

A

24 days

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15
Q

At what point does the lower limb bud form>

A

28 days

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16
Q

What developmental name is given to the humerus?

A

stylopod

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17
Q

What developmental name is given to the forearm?

A

zeugopod

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18
Q

What developmental name is given to the hand?

A

auto pod

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19
Q

What induces a limb bud to form? What kind of signalling is happening?

A

Fgf10 from lateral plate mesoderm activates Wnt

These Wnt’s then induce Fgf8 in the ectoderm (the growing part of the limb bud)

Fgf8 causes production of more Fgf10

This creates a positive feedback loop

20
Q

What is proximal distal outgrowth of the limb bud controlled by?

A

Apical Ectodermal Ridge (AER)

21
Q

What does the Apical Ectodermal Ridge secrete? (AER)? What is the function of the secretion?

A

Fibroblast growth factor 8 (FGF8)

FGF8 can mimic the AER by inducing supernumerary limbs

22
Q

What Hox paralogs give rise to the stylopod?

A

Hox 9 - 10 Paralogs

23
Q

What Hox paralogs give rise to the Zeugopod?

A

Hox 11 Paralogs

24
Q

What Hox paralogs give rise to the Autopod?

A

Hox 12 - 13 paralogs

25
Q

Define Paralog?

A

genes that are related to each other because they come from a common ancestral DNA sequence

26
Q

Prior to limb bud outgrowth what is the one of the first directional restrictions seen?

A

Anterior posterior specification

27
Q

What decides the overall shape and direction of the limb bud?

A

Zone of Polarizing Activity (ZPA)

28
Q

What does the Zone of Polarizing Activity produce?

A

Sonic hedgehog (Shh)

29
Q

If you were to remove a Zone of Polarizing Activity (ZPA) and implant it into an anterior limb bud what would you expect to happen?

A

duplicate digits to the limb buds own ZPA would appear because of the additional ZPA

30
Q

What is the function of Bone Morphogenetic Protein (BMP)?

A

shapes our digits

High [BMP] leads to increased cell death (apoptosis)

31
Q

Prior to limb rotation what is the orientation of the ventral and dorsal surfaces of a limb bud?

A

ventral surface faces medially

dorsal surface faces laterally

32
Q

What does the dorsal muscle mass of a limb bud form?

A

upper limb –> extensors and suppinators

Lower limb –> extensors and abductors muscles

33
Q

What does the ventral muscle mass of a limb bud form?

A

upper limb –> flexors and pronators muscles

Lower limb –> flexors and adductor muscles

34
Q

How long does it take for a primary axial a. To establish itself in the limbs?

A

Upper limb - Day 30

Lower limb - Day 36

35
Q

What is Meromelia? What causes it?

A

absence of part of a limb

Caused by late FGF signalling or partial loss of FGF signaling

36
Q

What is Amelia? What causes it?

A

Absence of the entire limb

Caused by early loss of FGF signaling

37
Q

What is Polydactyly? What causes it?

A

presence of supernumerary digits

Caused by overexpression of Shh (creation of a 2nd ZPA)

38
Q

Adactyly vs. Syndactyly

A

Adactyly - absence of digits

Syndactyly - fusion of digits

39
Q

What is Phacomelia? What causes it?

A

Thalidomide Baby

partial loss of FGF signaling or Hox disruption

40
Q

What is Ectrodactyly?

A

“lobster claw”

split hand/foot deformity

41
Q

What does Shh dictate?

A

The ventral portion of the neuraltube

42
Q

What controls the dorsal-ventral axis?

A

Wnt7a - responsible for dorsal portion

Lack of wnt7A dictates ventral axis (and Shh)

43
Q

What controls Wnt7a release (turns on)?

A

Lmx1b

44
Q

Where do limb tendons arise from?

A

Lateral plate mesoderm

45
Q

What artery branches of the aorta to join the primary axial a. Of the upper limb?

A

7th cervical intersegmental a.

46
Q

What artery branches of the aorta to join the primary axial a. Of the lower limb?

A

5th lumbar intersegmental a.

MSK - Final (23 decks)

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