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MSK-1 Test 1 > Limb Development > Flashcards

Limb Development Flashcards

1
Q

What is the middle limb bud structure? What does it become?

A

Zeugopod
becomes radius and ulna
tibia and fibula

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2
Q

What is meromelia? When does it occur?

A

missing part of limbs

week 4-8 messed up

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3
Q

What is the development of upper limb arteries?

A

dorsal aorta –> intersegmental arteries –> primary axial artery –> brachial artery –> remodeling to adult vasculature

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4
Q

What maintains the dorsal surface of developing limbs?

A

Wnt7

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5
Q

What happens if you upregulate the ZPA?

A

additional posterior elements (polydactyly)

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6
Q

What is the posterior side of a developing limb?

A

pinky side

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7
Q

What myotomes do leg musculature come from?

A

lumbar myotomes

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8
Q

What is the most proximal limb bud structure? What does it become?

A

stylopod

becomes humerus and femur

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9
Q

What germ cells do cartilage and connective tissue of the limbs come from?

A

somatic lateral plate mesoderm

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10
Q

What sex is more likely to have club foot?

A

males

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11
Q

What happens in the 5th week of development?

A

hand and foot plates form

chondrification centers appear

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12
Q

What is developmental hip dysplasia?

A

underdevelopment of the acetabulum of the hip bone

generalized joint laxity

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13
Q

Which direction do lower limb buds turn?

A

90 degrees medially

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14
Q

What is the development of lower limb arteries?

A

dorsal aorta –> intersegmental arteries –> primary axial artery –> deep artery of thigh –> remodeling to normal vasculature

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15
Q

What is FGF-10?

What does it do?

A

signal released by limb-forming mesoderm

stimulates overlying ectoderm to become Apical-ectodermal ridge

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16
Q

What is the anterior side of a developing limb?

A

thumb side

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17
Q

What myotomes are upper limb muscles from?

A

cervical myotomes

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18
Q

What is syndactyly? What causes it?

A

webbed fingers/toes

not enough BMPs in week 8

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19
Q

What signal tells embryo to selectively apoptose cells to create separate digits?

A

BMPs

20
Q

When does the first ossification occur?

A

12th week

21
Q

what genes control positioning of limbs along the craniocaudal axis?

A

Hox genes

22
Q

What do sensory axons follow to innervate limbs?

What sensory axons derive from?

A

follow motor axons

derived from neural crest cells

23
Q

What happens if you duplicate the ZPA?

A

duplication of posterior elemnts

24
Q

When do motor axons from the spinal cord enter the limb buds?

A

5th week

25
Q

What is club foot? What is it caused by?

A

all anatomical structures are present, but sole of foot turned medially and dorsiflexed
caused by limb rotation problem or too little amniotic fluid

26
Q

What is arthrogryposis? What is it caused by?

A

congenital joint contractures –> diminished range of motion in joints
causes are unclear but thought to be due to:
neuro defects, muscular abnormalities, joint tissue problems, fetal crowding

27
Q

What sets up dorso-ventral patterning signals (BMps and Wnt7)?

A

AER (apical ectodermal ridge)

28
Q

What happens in the 8th week?

A

separate digits formed

apoptosis mediated by BMPs to separate digits

29
Q

When do the limb buds form?

A

4th week

30
Q

What happens if you lose the ZPA?

A

loss of posterior limb elements

31
Q

Are anterior or posterior elements formed first? Why is that important?

A

Posterior formed first

If you lose P elements, can screw up whole A-P patterning and lose anterior elements too

32
Q

What signals does the Apical-Ectodermal Ridge release? What do they do?

A

FGF-8 and FGF-4

stimulate limb-bud mesoderm to grow; pattern it on proximo-distal axis

33
Q

Which direction do upper limb buds turn?

A

90 degrees laterally

34
Q

What sets up anterior-posterior pattering of limb (pinky to thumb)?
Where is it?

A

Zone of Polarizing Activity (ZPA)

On posterior side (little finger side)

35
Q

What happens in the 7th week?

A

digital rays of FEET
osteogenesis of long bones begins
rotation of limbs

36
Q

What sex is more likely to have developmental hip dysplasia?

A

females

37
Q

what happens in the 6th week?

A

digital rays of HANDS

entire limb skeleton is cartilaginous

38
Q

What is the most distal limb bud structure? What does it become?

A

autopod
becomes carpals, metacarpals, digits
tarsals, metatarsals, digits

39
Q

What is amelia?

A

no upper limbs at all
50s/60s: thalidimide

week 4

40
Q

What is ectrodactyly? What causes it?

A

lobster claw or split hand/foot

genetic: center of AER is not active/doesn’t exist –> middle digits don’t form = 4th week?

41
Q

What genes helps pattern mesoderm to become bones of upper extremity limbs?

A

Hox genes

42
Q

When does polydactyly occur?

A

week 6-7

43
Q

What maintains the ventral surface of limb development?

A

BMPs

44
Q

What signals does the ZPA release? What do those signal do?

A

Shh and retinoic acid

signal posterior elements (pinky)

45
Q

When do limb buds rotate?

A

week 7

46
Q

what is brachydactyly? What causes it?

A

Shortened digits

decreased FGF 4, 8, and 10 signaling in week 7 and 8

MSK-1 Test 1 (18 decks)

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