Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

control and movement > Lecture 1: Limb development > Flashcards

Lecture 1: Limb development Flashcards

embryology of upper limb development

1
Q

what are HOX genes?

A

primitive set of genes that are involved in determining structural differentiation in the body during development.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what happens when there is an abnormality in the HOX gene?

A

abnormalities in developement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is polydactyly?

A

extra digits

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is nail patella syndrome?

A

under development of structures n the back of the hand, arms, legs
(affects whole dorsum)
The nails are very small and missing patella are key characteristics.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

when do limb out-pouches develop?

A

week 5

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what are the limb pouches like in week 6?

A

slender and look like the upper limb

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are the limb pouches like in week 8?

A

fully developed limb (smaller scale)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

name the different parts of the mesoderm?

A
  1. paraxial mesoderm/somite
  2. intermediate mesoderm
  3. lateral plate mesoderm
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what do the somites develop into?

A

limb muscles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what do the lateral plate mesoderm develop into?

A

limb bones and connective tissues

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are the divisions of a somite called?

A

sclerotome - ventral-anterior (ventral column)

dermomyotome - dorso-lateral

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what are the sub-divisions of the dermomyotome?

A

dermatome - dermis of skin

myotome - skeletal muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what does the dorsal myotome give rise to?

A

back muscles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what does the anterior myotome give rise to?

A

muscles on ventral wall

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the nerve supply to the back muscles?

A

dorsi rami of spinal nerves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is the nerve supply to the thoracic and abdominal wall muscles?

A

ventral rami of spinal nerves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what are limb buds?

A

outpouching from the ventrolateral body wall

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what do the limb buds initially contain?

A

core tissue from lateral plate mesoderm.

this lateral plate mesoderm migrates into the limb bud and start to pattern out tendons and bones –> template for the limbs.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is the loose mesenchyme of the limb bud covered by?

A

ectoderm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what does the mesoderm core differentiate into?

A

bones and connective tissue of the limb

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what happens to the mesoderm that migrates to from the limb muscles?

A

divides into 2 parts:
1 . posterior condensation
2. Anterior condensation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what does the posterior condensation differentiate into?

A
  • extensors and supinators of upper limb

- extensors and abductors of lower limb

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what does the anterior condensation differentiate into?

A
  • flexors and pronators of upper limb

- flexors and adductors of lower limb

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what branch of the spinal cord give branches to innervate the upper limb buds?

A

ventral primary rami of spinal nerves C5-T1 (brachial plexus)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what branch of the spinal cord give branches to innervate the lower limb buds?

A

ventral primary rami of spinal nerves L1-S3 (lumbosacral plexus)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

which direction do the lower limbs rotate during development?

A

inwards

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

which direction do the upper limbs rotate during development?

A

outwards

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

how many axes do limbs develop along?

A

3

29
Q

what are the axes for limb development

A
  • Proximodistal – from the shoulder to the hand (and from the hip to the foot) - growth in length
  • Craniocaudal – head to toe growth. thumb grows on radial (lateral) side and little finger develops medially
  • Dorsoventral – the palm of the hand and sole of the foot are ventral and the knuckle side of the hand and foot are dorsal
30
Q

what is proximodistal outgrowth?

A

growth from proximal to distal

31
Q

what is FGF10?

A

fibroblast growth factor.

factor secreted by the mesenchumal core of the limb buds

32
Q

what is AER?

A

apical ectodermal ridge.

overlying ectoderm along the tip of the limb bud

33
Q

what is the function of FGF?

A

induces ridge of cells on the very distal end of developing limb (AER).

34
Q

what factors does the AER express?

A

FGF 4 + 8

35
Q

what is the function of FGF4 + 8

A

cause rapid proliferation of mesenchymal cells underlying the AER – the progress zone.

36
Q

what does the proximal zone do?

A

maintains proximodistal outgrowth of the imb

37
Q

what is FGF10 expressed by?

A

mesoderm

38
Q

what happens if AER is removed?

A

development is stopped

39
Q

what conditions occur if AER is removed?

A
  • Meromelia

- Amelia

40
Q

what is Meromelia? cause?

A

partial absence of a limb.

late or partial loss of FGF signalling/ AER disruption = arrest of proximodistal outgrowth.
can also be caused by vascular abnormalities

41
Q

what is Amelia? cause?

A

complete absence of limb.

early failure of FGF signalling/ the AER. The progress zone does not develop and there no proximodistal outgrowth.

42
Q

what is Cleft hand/foot?cause

A

Split hand/foot.

failure of the middle of the AER to develop properly

43
Q

what happens when central AER is missing?

A

Clefting of hand or foot

44
Q

what is ectopic FGF?

A

induces supernumerary limbs

45
Q

what is supernumerary limbs? cause?

A 
extra limbs
cause:
-genetic
-environmental 
-(exact cause unknown)
46
Q

what is craniocaudal patterning?

A

explains why the thumb is lateral and the little finger is medial

47
Q

what determines craniocaudal patterning?

A

zone of polarising activity

48
Q

what is the zone of polarising activity (ZPA)?

A

small region of mesenchume in the caudal part of the limb bud responsible for determining craniocaudal patterning

49
Q

where is sonic hedgehog is expressed?

A

the zone of polarising activity.

50
Q

what is sonic hedgehog?

A

diffuses from the ZPA in a cranial direction.

51
Q

what does high Conc. of SHH induce?

A

caudal structures e.g. little finger

52
Q

what does low Conc. of SHH induce?

A

cranial structures e.g. thumb

53
Q

what happens if there is inappropriate/ectopic SHH expression?

A

two sets of digits in a mirror pattern (polydactyly)

-mirror image because of diffusion gradient

54
Q

what does the dorsal ectoderm express?

A

Wnt7

55
Q

what does Wnt7 induce?

A

activation of the gene LMX1

56
Q

what does LMX1 essential for?

A

specifies the development of cells that become dorsal structures.

57
Q

what do the ventral ectoderm express?

A

Engrailed-1

58
Q

what does Englrailed-1 inhibit?

A

Wnt7

inhibit the development of dorsal structures on ventral side.

59
Q

Nail patella syndrome

what is the defect?

Main characteristics?

A
  • Rare syndrome affecting nails, bones, kidneys, and eyes
  • defect in LMX-1 B gene
  • absent or small, irregular patellae, abnormal nails.
60
Q

what happens to the digits in week 6?

A

terminal portion of limb buds flatten to form hand and foot plates

61
Q

how are digits formed?

A

selective apoptosis
-the digits form because of apoptosis in the centre. however, there are still growth of fingers because of AER in split into 5 portions.

62
Q

syndactyly

A

fused digits due to failure of normal apoptosis

63
Q

which drugs affect normal limb development

A

Teratogens:

  • Thalodomide –> was used to cure mornig sickness
  • sodium valproate —> antiepileptic
  • warfarin
  • cyproterine acetate –> potent steroidal ani-androgen used for severe achne –> Vitamin K (?)
  • NSAIDS–> premature risk of closure of the dugs arteriosus, risk of miscarriage
  • radiation, agent orange
  • environment: smoking/drinking
64
Q

what other factors affect normal limb development?

A
  • genetics–> hereditary or spontaneous mutations
  • maternal illness
  • amniotic band syndrome
  • unknown cause in many cases
65
Q

Achondraplasia

A

long bones of the limbs are shorter

66
Q

Amniotic band syndrome

A

bits of the placenta get tangled in the digits/limb = cut off blood supply

67
Q

phocomelia

A
  • digits develops prematurely

- proximal elements of limb absent

68
Q

what are the causes of phocomelia?

A
  • genetic factors

- teratogens –> commenly thalidomide (inhibits the expression of FGF10 and 8 and thoughts to inhibit angiogenesis)

69
Q

what is thalidomide still used for?

A

leprosy –> chronic, progressive bacterial infections (bacteria: mycobacterium leprae)

multiple myeloma –> cancer of plasma cells

used with access to strong contraceptives

control and movement (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions