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RDS Test 2 > B8.031 Embryogenesis > Flashcards

B8.031 Embryogenesis Flashcards

1
Q

fertilization and implantation time frame

A

weeks 1-2

blastocyst normally implants in uterus

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2
Q

embryonic period

A

week 3-8
in first 8 weeks, embryos progress from a single cell to having established organ primordia and “recognizable” external body form

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3
Q

fetal period

A

week 9-birth (40)

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4
Q

extraembryonic membrane formation (big picture)

A

membranes protect and nurture the developing embryo; function in gas & waste exchange
shock absorber

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5
Q

placentation (big picture)

A

placenta formation nutrition and waste exchange with embryo

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6
Q

gastrulation (big picture)

A

forms 3 germ layers, which give rise to body structures via cell proliferation, migration, differentiation, and morphogenesis (big scale movement of tissues)

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7
Q

cardiovascular development and hematopoiesis (big picture)

A

oxygenation and nutrition (along with placenta)

blood cell formation

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8
Q

neurulation (big picture)

A

formation of the nervous system

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9
Q

when does implantation occur

A

5.5-6 days

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10
Q

what cavities are present in the developing embryo at the end of the 2nd month

A

amniotic
chorionic
yolk sac
uterine

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11
Q

blastocyst development at day 4.5 to 5

A

composed of:
1. outer cell mass = trophoblast cells
2. inner cell mass = embyoblast, localized to one pole
fluid penetration into intercellular spaces of ICM results in blastocele cavity

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12
Q

2 layers of embryoblast

A

epiblast (upper)

hypoblast (lower)

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13
Q

cavities present in blastocyst at day 7.5

A

blastocyst and amniotic cavities

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14
Q

structure of epiblast

A

high columnar cells adjacent to amniotic cavity

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15
Q

amnioblasts

A

subset of epiblast cells adjacent to cytotrophoblast

secrete amniotic fluid

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16
Q

structure of hypoblast

A

cuboidal cells adjacent to blastocyst cavity

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17
Q

what occurs around day 9

A

deeper embedment

transformed blastocyst cavity emerges

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18
Q

what is the exocoelomic cavity and its function

A

primitive yolk sac
plays early role in nutrition
later connects to umbilical cord by a yolk stalk

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19
Q

primitive yolk sac membrane

A

exocoelomic (Heusers) membrane

formed from hypoblast

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20
Q

what occurs around day 12

A

extraembryonic (chorionic) cavity forms; filled with 2 layers of extraembryonic mesoderm
origin: lining of the exocoelomic cavity

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21
Q

layers of extraembryonic mesoderm in the chorionic cavity

A
  1. extraembryonic splanchnopleuric mesoderm: covers yolk sac

2. extraembryoinc somatopleuric mesoderm: lines cytotrophoblast layer

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22
Q

what occurs on day 13

A

secondary yolk sac forms within and obliterates the exocoelomic cavity

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23
Q

exocoelomic cyst

A

remnants of exocoelomic cavity that are “pinched off”

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24
Q

what surrounds the secondary yolk sac

A

lined with extraembryoinc endoderm (from hypoblast)

surrounded by extraembryonic splanchnopleuric mesoderm

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25
Q

what lines the amniotic cavity

A

amnion (inner fetal membrane)

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26
Q

what lines the chorionic (extraembryonic) cavity

A

extraembryoinc somatopleuric mesoderm

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27
Q

purpose of gastrulation

A

goes from a bilaminar to a trilaminar germ disc

ectoderm, mesoderm, endoderm

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28
Q

beginning of gastrulation

A

primitive streak (furrow on upper surface) forms on epiblast around the tail of the embryo

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29
Q

process of invagination in gastrulation

A

invagination of a subset of epiblast cells

  • subset of the invaginated cells displace hypoblast, creating the endoderm (ventral layer)
  • subset of invaginating cells lie between epiblast and endoderm/hypoblast creating mesoderm
  • epiblast cells remaining form ectoderm (dorsal)
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30
Q

how is gastrulation organized

A

primitive node

cells in epiblast that form elevated cluster at cranial margin of streak

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31
Q

when does gastrulation occur

A

starts week 3, continues through the end of the 4th week

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32
Q

how does the primitive node organize gastrulation

A

acts as a signaling center to pattern germ layers

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33
Q

movement of primitive streak

A

extends cranially, then regresses caudally

does NOT move up into head

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34
Q

describe the movement of cells in invagination

A

cells move lateral and cranial, influenced by signaling

  • chemo attractive in perimeter
  • chemo repulsive at midline
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35
Q

why is embryonic disc thickest at midline

A

this is where ingression is occuring

mesoderm only exists here before it has the chance to migrate out

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36
Q

eventual fate of the hypoblast

A

replaced by invaginating cells that form the endoderm

may contribute to lining of primitive yolk sac and extraembryonic endoderm and mesoderm

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37
Q

fate of epiblast cells

A

where epiblast cells migrate through primitive streak determines where cells will end up and what structures they will form

  • notochord
  • somites
  • urogenital system
  • body wall
  • chorion
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38
Q

formation of the notochord overview

A

prenotochordal cells that ingress through the primitive streak form the notochordal process (a hollow tube)
notochordal process flattens and some cells remain in the mesodermal layer; others intercalate in the hypoblast to form the notochordal plate

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39
Q

what 2 cell layers make up the notochord

A 
mesodermal
hypoblast (endoderm)
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40
Q

notochordal plate

A

cells proliferate and detach from the endoderm (as it replaces the hypoblast) and roll up to form a solid cord of cells

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41
Q

establishment of body axes

A
  1. left right
  2. dorsal ventral
  3. anterior posterior
    occurs before and during gastrulation
    results in embryonic asymmetry
    abnormalities of axes formation results in developmental malformations
42
Q

axis patterning genes in the anterior-posterior axis

A

AVE (anterior visceral endoderm)- acts with primitive node as a second signaling region in head
-expresses genes essential for head formation and other genes that inhibit formation of the primitive streak in the head

43
Q

when is the cranial end of the embryo established

A

before gastrulation

44
Q

what maintains the primitive streak (posterior embryo)

A

nodal

45
Q

ventralization signaling

A

BMP4 (secreted throughout embryonic disc) ventralizes mesoderm; forms intermediate and lateral plate mesoderm

46
Q

dorsalization signaling

A

chordin, noggin, and follistatin (secreted by node and prechordal mesoderm) antagonize BMP4 and thus dorsalize cranial mesoderm to form notocord from notochordal plate and paraxial mesoderm

47
Q

dorsal-ventral axis formation at later stage

A

after notochord is formed - chordin, noggin, and follistatin are expressed by notochord and play a role in neural induction in CRANIAL region
brachyury (T) gene dorsalizes mesoderm in middle and CAUDAL embryo forming paraxial mesoderm

48
Q

where is brachyury (T) gene expressed

A

node
notochordal precursor cells
notochord

49
Q

goosecoid

A

dorsalizes cranial/head mesoderm

activates chordin

50
Q

over/under expression of goosecoid

A

head malformations similar to conjoined twins phenotype

51
Q

function of brachyury (T) gene

A

essential for cell migration through primitive streak (mesoderm formation)
AND dorsalizing mesoderm (paraxial mesoderm formation)

52
Q

absence of brachyury (T) gene

A

decreased formation of mesoderm & decreased PA mesoderm (ie somites)
results in shortening of embryonic axis (caudal dysgenesis) that may result in fusion of the limb buds

53
Q

axis patterning for the left-right axis

A

gene cascade initiated by FGF8 on the L side establishes expression of nodal on the L
SHH represses L sidedness genes on the R

54
Q

how are cilia related to left-right axis formation

A

node contains ciliated cells; cilia rotate and set up directional fluid flow (signaling) patterns

55
Q

situs inversus

A

transposition of viscera in thorax and abdomen

linked to altered fluid flow

56
Q

when does cephalocaudal differentiation occur

A

mid 3rd week to mid 4th week

**gastrulation is still occurring caudally while differentiation is occuring cranially

57
Q

when does the primitive streak stop supplying cells

A

regresses caudally until the end of the 4th week

58
Q

why does the embryonic disc expand mainly in the cranial region

A

continuous migration of cells from the primitive streak in the cranial direction

59
Q

association between teratogenesis and gastrulation

A

in 3rd week, when gastrulation begins, embryo is highly sensitive to teratogenic insult

60
Q

holoprosencephaly

A

high doses of alcohol (consumed before mother knows she is pregnancy) lead to craniofacial malformations

61
Q

when are holoprosencephaly defects initiated

A

days 19-21

when midline of the forebrain is established

62
Q

features of holoprosencephaly

A

small forebrain
lateral brain ventricles fuse
fusion of lateral nasal prominences
failure of eye fields to separate properly

63
Q

what is a sacrococcygeal teratoma

A

results from remnants of the primitive streak in the sacrococcygeal region
may contain tissues derived from all 3 germ layers

64
Q

epidemiology of sacrococcygeal teratoma

A

more often observed in females

rare: 1 in 37,000

65
Q

mature sacrococcygeal teratoma characteristics

A

cystic: enclosed in its own fluid containing sac
solid: made up of tissue, but not self enclosed
mixed: containing both solid and cystic parts
typically NOT malignant

66
Q

cardiovascular system at the end of the 3rd week

A

villus capillaries contact vessels in the chorionic plate and connecting stalk, which in turn contact intraembryonic vessels

67
Q

when is the villous capillary system ready for heartbeat

A

4th week of development

68
Q

intermediate mesoderm derivatives

A

kidney

gonads

69
Q

paraxial mesoderm derivatives

A 
head
somite
-sclerotome
-myotome
-dermatome
70
Q

lateral mesoderm derivatives

A

splanchnic (visceral/organs)
somatic (body)
extra-embryonic

71
Q

derivates of the somite

A

vertebrae and ribs (bones) - sclerotome
dermis of the skin and back - dermatome
skeletal muscles of the back, body wall, and limbs - myotome

72
Q

overview of the urogenital system formation

A

3 overlapping kidney systems are formed cranial to caudal

  • pronephric
  • mesonephric
  • metanephric
73
Q

cloaca

A

common embryological cavity

excretory ducts of both the urinary and genital systems enter here

74
Q

heart formation in weeks 3-4

A

lateral folding results in cardiac tube formation

75
Q

vasculogenesis

A

de novo formation of endothelial tubes

76
Q

angiogenesis

A

sprouting of tubes off existing vessels

77
Q

what are hemangioblasts

A

common mesodermal precursors for blood cells (hematopoietic cells) and endothelial cells (angioblasts); located in blood islands

78
Q

what cell types are needed for vasculogenesis

A

both blood cells and endothelial cells

79
Q

what are blood islands

A

endothelial and blood cell precursors present in the wall of the yolk sac

80
Q

intraembryonic vascular formation

A

from splanchnic LPM

occurs slightly after extraembryonic vessel formation (from somatic and splanchnic extraembryonic mesoderm)

81
Q

site changing through the process of hematopoiesis

A
  • *blood cells initially form from splanchnic mesoderm**
    1. extraembryonic: blood islands of yolk sac; transitory (week 3)
    2. aorta-gonad-mesonephros region
    3. liver: colonized by cells from the AGM (2-7 months)
    4. bone marrow: colonized by cells from the liver; definitive (7th month of gestation)
82
Q

capillary hemangiomas

A

occur in 10% of births
may occur anywhere; but often in craniofacial regions
can be focal or diffuse
can disappear without treatment

83
Q

ectodermal derivatives

A

neural tube
neural crest (epithelial to mesenchymal transformation)
epidermis
sweat glands and hair follicles

84
Q

derivatives of the endodermal germ layer

A

epithelial lining of: GI tact, respiratory tract, urinary bladder, auditory tube, liver, pancreas, cloaca

85
Q

gut formation from endoderm and cephalocaudal folding

A

embryonic disc begins to bulge in amniotic cavity as result of brain vesicle growth
folding is most pronounced in head and tail
cephalocaudal folding promotes endoderm lined cavity incorporated into embryo body

86
Q

formation of umbilical cord

A

portion of the allantois (evagination of hindgut) is surrounded by mesoderm of connecting stalk
together form umbilical cord
blood vessels form from mesoderm

87
Q

foregut

A

bounded by buccopharyngeal membrane until its rupture in 4th week

88
Q

midgut

A

temporarily communicates with yolk sac

89
Q

hindgut

A

terminates temporarily at cloacal membrane until its rupture in 7th week

90
Q

function of lateral folding in formation of the gut tube and ventral body wall

A

lateral folding results from rapid growth of somites
embryo assumes rounded appearance
gut forms tube and ventral body wall is established
midgut connection with yolk sac becomes long and narrow (vitelline duct)

91
Q

relationship of gut to umbilical cord

A

at 10 weeks; intestinal loops are herniated into the yolk sac DUCT and are in the umbilical cord due to size constraints of the abdominal cavity

92
Q

defects of the ventral body wall

A 
failure to close after lateral folding
ectopia cordis (ectopic heart)
bladder exstrophy
gastroschisis
cloacal exstrophy
93
Q

bladder exstrophy

A

eversion; failure of pelvic region to close

94
Q

gastroschisis

A

herniation of intestines through abdominal wall

95
Q

cloacal exstrophy

A

failure of pelvic region to close

96
Q

diagnosis of ventral body wall defects

A
  1. presence of high maternal serum AFP levels (similar to spina bifida)
  2. US imaging
97
Q

respiratory development overview

A

25 days
epithelial lining of larynx, trachea, bronchi, and lungs is endodermal in origin
respiratory diverticulum/lung bud is outgrowth from ventral wall of foregut (4 weeks)
tracheoesophageal septum later divides foregut into: dorsal esophagus, ventral trachea, lung buds

98
Q

what are the pharyngeal arches

A

5 paired structures surrounding the pharynx
form MSK structures in head and neck
resembles gill formation in fishes and amphibians

99
Q

derivation of pharyngeal arches

A

derived from paraxial mesoderm (somitomeres and occipital somites) and neural crest cells
covered with ectoderm, lined by endoderm

100
Q

what do the pharyngeal arches contribute to

A

formation of face, neck, mouth, larynx, pharynx

muscles, arteries, connective tissue, cartilage, parts of skeleton

101
Q

when does external body form development take place

A

7-8th week development
limbs have 3 segments
most major organs and organ systems formed

RDS Test 2 (24 decks)

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