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Embryo > M01: THIRD WEEK OF DEVELOPMENT: TRILAMINAR GERM > Flashcards

M01: THIRD WEEK OF DEVELOPMENT: TRILAMINAR GERM Flashcards

1
Q

process whereby the bilaminar embryonic disc undergoes reorganization to form a trilaminar disc

A

GASTRULATION

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2
Q

throughout the gastrulation, ectoderm continuous to form the ___to the ___ end of embryo

A

cranial

caudal

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3
Q

what are the three distinct primary germ layers established during gastrulation

A

ectoderm, mesoderm, and endoderm

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4
Q

Marks the end of gastrulation

A

establishment of three distinct primary germ layers throughout the whole embryonic disc

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5
Q

GASTRULATION begins with the ___formation on the surface of the epiblast

A

primitive streak

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6
Q

what day does the bilaminar embryonic disc, consisting of hypoblast and epiblast has formed

A

day 14

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7
Q

composition of bilaminar embryonic disc at day 14 (2)

A

hypoblast and epiblast

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8
Q

what day does A thickened structure formed along the midline in the epiblast near caudal end of bilaminar embryonic disc

A

day 15

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9
Q

this is the midline formed in the epiblast near caudal end of bilaminar embryonic disc

A

the primitive streak

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10
Q

where primitive streak is formed

A

midline of the epiblast

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11
Q

At what day does the primitive Streak visible as a narrow groove

A

day 15 and 16

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12
Q

It defines the major body axis of embryo

A

primitive streak

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13
Q

what major body axes are defined by primitive streak

A

 cranial end- towards the head
 caudal end- towards the tail
 left and right side of embryo

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14
Q

the primitive streak expands to create a what?

A

primitive node

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15
Q

what is the circular depression content of primitive node

A

primitive pit

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16
Q

T/F, The primitive pit is continuous with the primitive groove,

A

true

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17
Q

the primitive groove runs {caudally/cranially} along the midline of the primitive streak.

A

caudally

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18
Q

A process where cells of the epiblast migrate inwards towards the streak; they detach from the epiblast, and slip beneath into the interior of the embryonic disc

A

invagination

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19
Q

Invagination occurs before primitive groove is formed, T/F

A

false, after

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20
Q

It controls cell migration and specification

A

Fibroblast Growth Factor 8 (FGF8)

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21
Q

(FGF8) is synthesized by?

A

streak cells

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22
Q

• Cell movement control through down-regulation of what protein?

A

E-cadherin

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23
Q

protein that binds epiblast cells together

A

E-cadherin

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24
Q

Cell specification control into the mesoderm through ___expression regulation

A

BRACHYURY (T)

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25
Q

The first cells to invaginate through primitive node invade the ____and displace its cells.

A

hypoblast

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26
Q

the new proximal cell layer which replaces the hypoblast cells completely

A

Definitive endoderm

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27
Q

what day is • majority of hypoblast has been replaced

A

day 16

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28
Q

is the remaining cells of epiblast, which forms the most exterior, distal layer

A

Ectoderm

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29
Q

the invaginated epiblast cells that remain between ectoderm and newly formed definitive endoderm will form a layer called

A

mesoderm

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30
Q

Layer which subsequently forms the notochord

A

mesoderm

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31
Q

notochord

A

the basis for the axial skeleton.

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32
Q

Once the formation of the definitive endoderm and mesoderm is complete, ____ no longer migrate towards the primitive streak

A

epiblast cells

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33
Q

the remaining cells of the epiblast which forms the third germ layer

A

ectoderm

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34
Q

by the end of the ___week, the three primary germ layers complete the embryonic disc.

A

third

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35
Q

what is displaced in the formation of endoderm

A

hypoblast

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36
Q

 Once cells are invaginated, some cells displace the hypoblast, forming what layer

A

endoderm

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37
Q

Seen in between the epiblast and newly formed endoderm

A

mesoderm

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38
Q

Remaining cells in epiblast create what?

A

ectoderm

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39
Q

As more cells migrate to epiblast and hypoblast layers, they spread __and __ (direction)

A

laterally

cranially

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40
Q

Cell migrate gradually beyond disc margin and establish contact with ___

A

extraembryonic mesoderm

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41
Q

covers yolk sac and amnion

A

extraembryonic mesoderm

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42
Q

direction at which cells pass at each side of prechordal plate

A

Cephalic direction

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43
Q

important for forebrain induction

A

prechordal plate

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44
Q

formed between tip of notochord and oropharyngeal membrane

A

prechordal plate

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45
Q

contains a small region of tightly adherent ectoderm and endoderm cells

A

Oropharyngeal membrane

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46
Q

location of Oropharyngeal membrane

A

at cranial end

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47
Q

future opening of oral cavity

A

tightly adherent ectoderm and endoderm cells of Oropharyngeal membrane

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48
Q

the stage of development where the neural plate forms the neural tube

A

Neurulation

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49
Q

mark the beginning of the formation of the central nervous system

A

Neurulation

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50
Q

The first event in neurulation is

A

formation of the neural plate.

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51
Q

thickened area of cells in neurolation

A

neural plate

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52
Q

At what day does the notochord induces the ectodermal cells lying just cranial to the primitive node to differentiate into columnar neuroepithelial cells

A

19 days after fertilization

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53
Q

A process in which notochord induces the ectodermal cells lying just cranial to the primitive node to differentiate into columnar neuroepithelial cells

A

neural induction

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54
Q

What will the ectodermal cells differentiate into during neural induction

A

columnar neuroepithelial cells

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55
Q

Invaginating pre-notochordal cells move forward cranially in the midline until they reach the ___

A

prechordal plate

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56
Q

they intercalate in hypoblast creating 2 transient layers that form notochord plate

A

Pre-notochordal cells

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57
Q

what forms during intercalation of pre-notochordal cells

A

notochord plate

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58
Q

cells moving in the streak replace the hypoblast during neurolation

A

Endoderm cells

59
Q

notochordal plate cells proliferate then detach from endoderm forming a solid cord of cells called

A

definitive notochord

60
Q

this underlies neural tube

A

definitive notochord

61
Q

Signaling center for inducing axial skeleton

A

definitive notochord

62
Q

T/F, Notochord formation is a static process

A

false, dynamic

63
Q

what forms first during notochord formation {cranial/caudal}

A

cranial end`

64
Q

They extend cranially to the prechordal plate during notchord formation

A

Notochord and prenotochordal plate

65
Q

area caudal to oropharyngeal membrane

A

prechordal plate

66
Q

Notochord and prenotochordal plate extend cranially to the ___and to ___caudally

A

prechordal plate

primitive pit

67
Q

This temporarily connects amniotic and yolk sac cavities

A

neurenteric canal

68
Q

formed from embryonic disc’s caudal end

A

Cloacal membrane

69
Q

similar structure to oropharyngeal membrane

A

Cloacal membrane

70
Q

Cloacal membrane contains {tightly/loosely} adherent ectoderm and endoderm cells with {no/rich} mesoderm

A

tightly

No

71
Q

Once cloacal membrane appears, the yolk sac’s {posterior/anterior} wall forms a small ___extending to connecting stalk

A

posterior

diverticulum

72
Q

What appears at 16th day of development during neurolation (2)

A

diverticulum, allantoenteric diverticulum, or allantois

73
Q

aka allantosis

A

allantoenteric diverticulum

74
Q

Lower vertebrates: ___as reservoir for excretion products of renal system

A

allantois

75
Q

In Humans, allantois, may be involved in bladder development abnormalities. T/F

A

true

76
Q

The neural plate forms at the ___of the embryo

A

cranial end

77
Q

indicates the region of the eventual brain

A

cranial end of the neural plate

78
Q

represents the eventual region of the spinal cord.

A

narrower caudal end

79
Q

By the end of the ___week of development, the lateral edges of the neural plate become elevated, and fold to form the neural fold

A

third

80
Q

the lateral edges of the neural plate become {elevated/depressed}, and fold to form the ___

A

elevated

neural fold

81
Q

The groove created by the folding of the neural plate is called

A

neural groove

82
Q

at what level of somite does the two neural folds approach each other

A

4th level

83
Q

Approximately ___after fertilization, the folds fuse together, and the neural plate transforms into the neural tube

A

25 days

84
Q

it is the precursor to the central nervous system

A

neural tube

85
Q

Fusion of the neural tube usually begins in the ___region

A

cervical

86
Q

The openings that are formed at the cranial and caudal ends of the embryo are called

A

cranial and caudal neuropores

87
Q

• During the closure of the neural tube, cells on the lateral side of the neural plate detach forming a new cell population, called

A

neural crest

88
Q

migrate and displace the cells of the ectoderm to enter the underlying mesoderm

A

neural crest cells

89
Q

neural crest cells contribute to the formation of (2)

A

peripheral nervous system,

formation of neurons and glial cells of the sympathetic, parasympathetic, and sensory nervous systems

90
Q

Marks the end process of neurulation

A

complete fusion of neural tube

91
Q

What are the body axes (3)

A

anterior posterior (A-P; craniocaudal),

dorso-ventral (D-V),

left-right (L-R)

92
Q

T/F, Establishment of body axes occurs late in embryogenesis

A

false, early

93
Q

Initiated during __stage with A-P and D-V axes specified prior to L-R

A

morula

94
Q

T/F, A-P and D-V axes specified prior to L-R

A

true

95
Q

A-P axis determined at what stage

A

blastocyst stage

96
Q

Cells from cranial end of endoderm layer of bilaminar disc migrate towards what will become the head region to form the

A

anterior visceral endoderm (AVE)

97
Q

At this bilaminar disc stage, cells from AVE express genes for head formation

A

anterior visceral endoderm (AVE)

98
Q

AVE includes (2)

A

Transcription factors

Secretion factors

99
Q

Transcription factors for AVE (3)

A

OTX2, LIM1, and HESX1

100
Q

Secretion factors for ave (2)

A

cerberus and leftyl (members of the TGF-β family)

101
Q

They inhibit nodal activity hence establishing cranial end of embryo

A

cerberus and leftyl

102
Q

T/F, Absence of cerberus and leftyl at caudal end inhibits nodal expression to continue;

A

false, allows

103
Q

T/F, Nodal expression will establish and maintains primitive streak

A

true

104
Q

It upregulates genes responsible for formation of dorsal and ventral mesoderm and head and tail structures

A

NODAL

105
Q

T/F, NODAL is member of TGF-alpha family

A

false, tgf-beta

106
Q

This is secreted throughout embryonic disc

A

Bone morphogenetic protein 4 (BMP4)

107
Q

combination in which mesoderm would be ventralized

A

BMP4 with FGF

108
Q

T/F, The node is the organizer

A

true

109
Q

Antagonistic genes of BMP4 (5)

A 
Chordin
Noggin
Follistatin
Nodal
goosechoid
110
Q

CHORDIN: activated by transcription factor __?

A

GOOSECOID

111
Q

In BMP4 antagonists, cranial mesoderm is dorsalized into (3)

A

notochord, somites, and somitomeres

112
Q

3 genes important for neural induction in the cranial region

A

notochord, somites, and somitomeres

113
Q

responsible for initiating and maintaining primitive streak

A

Nodal

114
Q

maintains node and later induces regional specificity in forebrain and midbrain areas

A

HNF-3β

115
Q

Absence of HNF-3β will result to (2)

A

embryos fail to gastrulate properly

lack forebrain and midbrain structures

116
Q

controls regulation of dorsal mesoderm formation

A

BRACHYURY (T) gene

117
Q

BRACHYURY (T) gene is expressed in the ___ (3)

A

node,

notochord precursor cells,

and notochord

118
Q

Responsible for cell migration through the primitive streak

A

BRACHYURY (T) gene

119
Q

BRACHYURY (T) gene encodes a sequence-specific DNA-binding protein that functions as a

A

transcription factor

120
Q

DNA-binding domain

A

T-box

121
Q

__genes in the T-box family

A

> 20

122
Q

Absence of T-box would result in

A

caudal dysgenesis

123
Q

embryonic axis shortening

A

caudal dysgenesis

124
Q

In caudal dysgenesis, Degree of shortening depends on time which protein becomes excessive . T/F

A

false, deficient

125
Q

Laterality or L-R sidedness also established in {early/late} development

A

early

126
Q

T/F, Normally, many organs exhibit asymmetries

A

true

127
Q

Organs that exhibit assymetries

A

• Heart, lungs, gut, spleen, stomach, liver, and others

128
Q

Once primitive streak appears, cells of the node and primitive streak secrete __

A

FGF8

129
Q

growth factor induces expression of NODAL

A

FGF8

130
Q

T/F, NODAL expression often restricted to right side of embryo

A

false, left

131
Q

Why is nodal expression often restricted to right side of embryo

A

due to serotonin (5-HT) accumulation on left side

132
Q

These establishes midline and prevent NODAL expression from crossing over to the right side (3)

A

SONIC HEDGEHOG (SHH),
LEFTY1,
ZIC3

133
Q

activates transcription factor MAD3 expression to the left side of primitive node

A

5-HT

134
Q

From the left lateral plate, Nodal protein initiates signal cascade with LEFTY2 to upregulate ___

A

PITX2

135
Q

Homeobox-containing transcription factor

A

PITX2

136
Q

Master gene for left-sidedness establishment

A

PITX2

137
Q

Promotes repeated expression in left side of heart, stomach, and gut primordial as they assume the normal asymmetrical body positions

A

PITX2

138
Q

T/F, Genes for right-side regulation not as well defined

A

true

139
Q

Transcription factor that is restricted to right lateral plate mesoderm

A

SNAIL

140
Q

 regulates effector genes for right side establishment

A

SNAIL

141
Q

T/F Cascade initiated to the left involve cilia on cells in the node

A

true

142
Q

establishes signaling gradient (2)

A

• gap junctions and small ion transport

143
Q

create gradient of NODAL towards the left

A

cilia on cells in the node

Embryo (2 decks)

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