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Control and Movement 2 > Movement Lecture 5: Limb embryology > Flashcards

Movement Lecture 5: Limb embryology Flashcards

1
Q

During which weeks of development does limb development occur?

A

Weeks 4-8

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2
Q

Which section of the mesoderm is the core tissue of the limb bud initially derived from?

A

Lateral plate mesoderm

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3
Q

What does the mesoderm differentiate into in the limb bud, and what will this eventually form?

A

Mesenchyme

Bones and connective tissue

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4
Q

Which section of the mesoderm is skeletal muscle derived from?

A

Paraxial mesoderm

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5
Q

Which section of the mesoderm forms somites?

A

Paraxial mesoderm

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6
Q

During which week do the somites divide to form a sclerotome and a dermomyotome?

A

Week 4

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7
Q

Which of the sclerotome and dermomyotome is formed by the ventral somite and which is formed by the dorsal somite?

A

Ventral somite -> sclerotome

Dorsal somite -> dermomyotome

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8
Q

What is formed from the sclerotomes?

A

Vertebral column

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9
Q

What is formed from the dermomyotomes?

A

Dermis of the skin and skeletal muscles

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10
Q

During which week do the myotomes divide?

A

Week 5

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11
Q

Which sections are formed by the division of the myotomes?

A

Epimere

Hypomere

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12
Q

Which of the epimere and hypomere is dorsal and which is ventral, and which muscles will they form?

A 
Epimere = dorsal, will form intrinsic back muscles that are innervated by the dorsal rami
Hypomere = ventral, will form all other skeletal muscle that is innervated by the ventral rami
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13
Q

By which week have the hypomeres formed anterior and posterior condensations?

A

Week 7

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14
Q

What is the general function of the muscles derived from the anterior condensation of the hypomere in the leg?

A

Flexors and adductors

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15
Q

What is the general function of the muscles derived from the posterior condensation of the hypomere in the leg?

A

Extensors and abductors

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16
Q

During which weeks do the limbs rotate?

A

Weeks 6-8

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17
Q

In which direction do the lower limbs rotate during development and by how many degrees?

A

90 degrees medially

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18
Q

Which tissue secretes Fgf10?

A

Mesenchyme

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19
Q

What is induced by Fgf10?

A

Formation of the ectoderm to form the apical ectodermal ridge at the tip of the limb bud

20
Q

Which fibroblast growth factors are produced by the apical ectodermal ridge?

A

Fgf 4 and 8

21
Q

What is induced by the fibroblast growth factors produced by the AER?

A

Mesenchyme proliferation to form the progress zone

22
Q

Which direction does the growth induced by Fgf10 occur in?

A

Proximodistal

23
Q

What condition is induced by introducing Fgf-soaked beads into an embryo?

A

Supernumeracy of the limbs

24
Q

In dorsoventral patterning, what is expressed by the dorsal ectoderm?

A

Wnt7

25
Q

In dorsoventral patterning, what is expressed by the ventral ectoderm?

A

Engrailed-1

26
Q

What is the effect of engrailed-1 on Wnt7?

A

Inhibitor

27
Q

Which of engrailed-1 and Wnt7 will cause the formation of the sole of the foot or the palm of the hand?

A

Engrailed-1

28
Q

What would happen to the foot if Wnt7 was improperly expressed?

A

Soles would form on both sides

29
Q

What is the area of the mesenchyme that controls craniocaudal patterning called?

A

Zone of polarising activity

30
Q

Is the zone of polarising activity located cranially or caudally in the limb bud?

A

Caudally

31
Q

What is expressed by the zone of polarising activity?

A

Sonic hedgehog (Shh)

32
Q

What does low concentrations of Shh induce?

A

Formation of cranial structures in the limb bud eg. thumbs and big toes

33
Q

What does high concentrations of Shh induce?

A

Formation of caudal structures in the limb bud eg. little fingers and toes

34
Q

What condition can be seen if the zone of polarising activity is transplanted so it is present both cranially and caudally in the limb bud?

A

Mirror image polydactyly

35
Q

During which week do the terminal limb buds flatten to form hand and foot plates?

A

Week 6

36
Q

What process in the AER causes digit formation?

A

Apoptosis

37
Q

What is the name for the complete absence of limbs?

A

Amelia

38
Q

What is amelia caused by?

A

Early loss of Fgf signalling

39
Q

What would cause meromelia?

A

Partial or late loss of Fgf signalling

40
Q

What is the name for the partial absence of limbs eg. only present up to the elbow?

A

Meromelia

41
Q

What is phocomelia?

A

Digits developing prematurely, with a lack of proximal limb structures
“Flipper limb”

42
Q

What malformation can be caused by thalidomide?

A

Phocomelia

43
Q

What does thalidomide inhibit?

A

Fgf 8+10

44
Q

What happens if apoptosis in the AER fails?

A

Syndactly - fused digits

45
Q

What is the name for the presence of extra digits and what causes it?

A

Polydactyly

Inappropriate Shh expression

46
Q

What is the medial name for a “lobster claw” deformity?

A

Ectrodactyly

47
Q

What malformation can develop when the middle of the AER fails to form properly

A

Ectrodactyly

Control and Movement 2 (22 decks)

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