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MSK exam 1 > embryo-limb development > Flashcards

embryo-limb development Flashcards

1
Q

two layers of a developing embryo

A

embryoblast

trophoblast

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2
Q

embryoblast forms

A

epiblast

hypoblast

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3
Q

trophoblast forms

A

syncytiotrophoblast

cytotrophoblast

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4
Q

what happens on day 16 of development?

A

gastrulation occurs

from bilaminar to trilaminar

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5
Q

three layers that result from gastrulation

A

endoderm
mesoderm (layer that forms due to gastrulation)
ectoderm

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6
Q

what occurs during neurulation

A

formation of neural tube

mesoderm forms paraxial, intermediate and lateral plate on either side of neural tube

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7
Q

paraxial mesoderm organizes into what

A

somitomeres that become somites

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8
Q

how many somites by day 35

A

42-44 somites

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9
Q

somitomeres in the head form

A

neuromeres not somites

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10
Q

somites from from which somitomeres

A

occipital region to caudal region

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11
Q

what are the regions of somites

A 
4 occipital
8 cervical
12 thoracic
5 lumbar
5 sacral
8-10 coccygeal

1st occipital and last 7 coccygeal disappear

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12
Q

what two layers do somites differentiate into

A

sclerotome

dermomyotome

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13
Q

what does the sclerotome give rise to

A 
vertebrae and most of skull
axial skeleton
rib
cartilage 
bones of the trunk
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14
Q

what do bones first appear as

A

condensations of mesenchyme cells

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15
Q

what are the two methods of bone development

A

intramembranous

endochondral

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16
Q

intramembranous

A

mesenchyme cells are just replaced by bone cells or osteocytes

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17
Q

endochondral

A

mesenchyme become chondrocytes then form bone cells or osteocytes

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18
Q

lateral plate mesoderm forms

A

sternum and limb bones

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19
Q

neural crest forms

A

bones of the skull

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20
Q

head somitomers form

A

forms the cranial vault and base of skull

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21
Q

what two layers does the dermomyotome give rise to

A

dermatome

myotome

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22
Q

dermatome gives rise to

A

dermis and subcutaneous tissue

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23
Q

myotome gives rise to

A

muscle

myoblasts fuse to form myotubes which fuse to form muscle fibers

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24
Q

abaxial muscle cell precursors form what

A

ventrolateral muscle cells
limb muscles
abdominal muscles
infrahyoid muscles

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25
Q

pimaxial muscle cell precursors from what

A

dorsomedial muscle cells
muscles of the back
shoulder girdle
intercostal muscles

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26
Q

muscle cells from the limbs are derived from

A

somites from specific segmental levels

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27
Q

epaxial

A

intrinsic back muscles

from primaxial

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28
Q

hypaxial

A

body wall and limb muscles

from abaxial

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29
Q

how do vertebral column forms from sclerotomes

A

caudal portion of each sclerotome proliferates and fuses with cranial portion of inferior sclerotome

intersegmental

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30
Q

notochord forms

A

nucleus pulposus

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31
Q

mesenchyme forms

A

annulus fibrosus

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32
Q

congenital scholiosis

A

asymmetric fusion of vertebra
appears that half of the vertebra is missing
abnormal curvature of the vertebral column

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33
Q

accessory ribs due to

A

extra vertebral body

34
Q

fused ribs due to

A

missing a vertebral body

35
Q

klippel-feil anomaly (brevicollis)

A

short neck because of the absence or fusion of cervical vertebra

at craniovertebral junction
1% of new borns

36
Q

how do limb buds appear

A

as outpocketings from ventrolateral body wall

37
Q

limb buds consist of

A

core of mesenchyme surrounded by surface ectoderm

38
Q

upper limb buds appear by day

A

day 26

39
Q

lower limb buds appear by day

A

day 28

40
Q

mesenchyme is

A

somatic layer of lateral plate mesoderm

41
Q

mesenchyme contributes to

A 
bones
tendons
ligaments
cartilage
fascia
joints
vessels
dermis
42
Q

homeobox (hox) gene does

A

regulates axes and patterning

43
Q

AER is essential for

A

the proximal-distal axis of limbs

44
Q

AER stands for

A

apical ectodermal ridge

45
Q

what forms AER

A

apex of each limb bud thickens to form, mutilayered

46
Q

AER induces

A

proliferation of underlying mesenchyme

47
Q

AER causes which mesenchyme to remain undifferentiated

A

adjacent mesenchyme

48
Q

ZPA is responsible for

A

patterning of the anterior-posterior axis of limbs

49
Q

how does ZPA form

A

mesenchymal cells aggregate at the posterior margin of the limb bud forming a zone of polarized activity

50
Q

retinoic acid

A

should not be taken during pregnancy. can cause duplication of limbs

normally cells in ZPA release it already

51
Q

hand and foot pads form

A

distal ends of the limb buds flatten

52
Q

what does mesenchyme do in hands and feet

A

mesenchyme condenses to form digital rays by 6th week for hands and 7th weeks for feet

53
Q

what causes formation of separate digits

A

apoptosis between digits

each finger still has AER to continue distal growth

54
Q

when does mesenchyme form cartilaginous models of the limb

A

6th week

mesenchyme to chondrocytes to cartilage

55
Q

when doe endochondral ossification begin to form limb bones from lateral plate mesoderm

A

8th week

56
Q

by what week have all bones form

A

12th week

57
Q

when does secondary ossification center form

A

at birth

58
Q

how do limbs rotate to each anatomical position

A

upper limbs rotate laterally through 90

lower limbs rotate medially almost 90

59
Q

how does dermatome start

A

segmentally then changes

60
Q

initial blood supply to upper limb

A

dorsal intersegmental arteries from aorta

61
Q

primordial vascular pattern consists of

A

primary axial arteries

62
Q

what does the axial artery become

A

brachial and then common interosseous

63
Q

what are the secondary branches from the brachial

A

radial and ulnar arteries

64
Q

which artery degenerates

A

median artery

65
Q

what does the axial artery begin as

A

ischiadic atery

66
Q

primary axial artery is represented by

A

profunda femoris
popliteal
posterior tibial

67
Q

minor limb anomalies are how common

A

fairly common

68
Q

what is critical period for limb anomalies

A

4th-5th weeks

69
Q

how often do major limb anomalies occure

A

1/500

usually genetics

70
Q

major cause of limb defects from 1957-1961

A

thalidomide

71
Q

bone malformations

A

failure to develop
formation of extra bones
fusion of adjacent digits

72
Q

achondroplasia

A

cause of dwarfism
1/15000
bowed limbs and short
disturbance of endchondral ossification at epiphyseal plates

73
Q

thanatophoric dysplasia

A

lethal skeletal dysplasia
1/20,000
respiratory failure
fibroblast growth factor receptor deficiency

74
Q

osteogenesis imperfecta

A

deficient in type 1 collagen

early hearing loss, protrusion of eyes, bowing of legs, fractures. blue-gray sclera.

75
Q

amelia

A

absence of entire limb

76
Q

meromelia

A

absence of part of limb

77
Q

cleft hand or foot (extrodactyly)

A

lobster claw deformity
absence of central digit
failure of digital rays to form

78
Q

brachydactyly

A

shortness of digits

associated with short stature

79
Q

polydactyly

A

supernumery digits
extra digits usually useless
extra digits is medial or lateral
toes not in center, useless

80
Q

syndactyly-two types

A

1/2200
webbed digits
cutaneous (webbing of digits)
osseous (fusion of bone)

81
Q

congenital clubfoot

A

generally any defect with talus
1/1000
abnormal orientation of the foot that prevents normal weight bearing
inconclusive evidence for restriction movement in utero as cause
environmental factors

82
Q

congenital dislocation of hip

A

1/1500

results from laxity of the joint capsule or underdevelopment of the acetabulum

MSK exam 1 (3 decks)

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