M01: THIRD WEEK OF DEVELOPMENT: TRILAMINAR GERM Flashcards
(143 cards)
1
Q
process whereby the bilaminar embryonic disc undergoes reorganization to form a trilaminar disc
A
GASTRULATION
2
Q
throughout the gastrulation, ectoderm continuous to form the ___to the ___ end of embryo
A
cranial
caudal
3
Q
what are the three distinct primary germ layers established during gastrulation
A
ectoderm, mesoderm, and endoderm
4
Q
Marks the end of gastrulation
A
establishment of three distinct primary germ layers throughout the whole embryonic disc
5
Q
GASTRULATION begins with the ___formation on the surface of the epiblast
A
primitive streak
6
Q
what day does the bilaminar embryonic disc, consisting of hypoblast and epiblast has formed
A
day 14
7
Q
composition of bilaminar embryonic disc at day 14 (2)
A
hypoblast and epiblast
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
9
Q
this is the midline formed in the epiblast near caudal end of bilaminar embryonic disc
A
the primitive streak
10
Q
where primitive streak is formed
A
midline of the epiblast
11
Q
At what day does the primitive Streak visible as a narrow groove
A
day 15 and 16
12
Q
It defines the major body axis of embryo
A
primitive streak
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
14
Q
the primitive streak expands to create a what?
A
primitive node
15
Q
what is the circular depression content of primitive node
A
primitive pit
16
Q
T/F, The primitive pit is continuous with the primitive groove,
A
true
17
Q
the primitive groove runs {caudally/cranially} along the midline of the primitive streak.
A
caudally
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
19
Q
Invagination occurs before primitive groove is formed, T/F
A
false, after
20
Q
It controls cell migration and specification
A
Fibroblast Growth Factor 8 (FGF8)
21
Q
(FGF8) is synthesized by?
A
streak cells
22
Q
• Cell movement control through down-regulation of what protein?
A
E-cadherin
23
Q
protein that binds epiblast cells together
A
E-cadherin
24
Q
Cell specification control into the mesoderm through ___expression regulation
A
BRACHYURY (T)
25
The first cells to invaginate through primitive node invade the ____and displace its cells.
hypoblast
26
the new proximal cell layer which replaces the hypoblast cells completely
Definitive endoderm
27
what day is • majority of hypoblast has been replaced
day 16
28
is the remaining cells of epiblast, which forms the most exterior, distal layer
Ectoderm
29
the invaginated epiblast cells that remain between ectoderm and newly formed definitive endoderm will form a layer called
mesoderm
30
Layer which subsequently forms the notochord
mesoderm
31
notochord
the basis for the axial skeleton.
32
Once the formation of the definitive endoderm and mesoderm is complete, ____ no longer migrate towards the primitive streak
epiblast cells
33
the remaining cells of the epiblast which forms the third germ layer
ectoderm
34
by the end of the ___week, the three primary germ layers complete the embryonic disc.
third
35
what is displaced in the formation of endoderm
hypoblast
36
Once cells are invaginated, some cells displace the hypoblast, forming what layer
endoderm
37
Seen in between the epiblast and newly formed endoderm
mesoderm
38
Remaining cells in epiblast create what?
ectoderm
39
As more cells migrate to epiblast and hypoblast layers, they spread __and __ (direction)
laterally
| cranially
40
Cell migrate gradually beyond disc margin and establish contact with ___
extraembryonic mesoderm
41
covers yolk sac and amnion
extraembryonic mesoderm
42
direction at which cells pass at each side of prechordal plate
Cephalic direction
43
important for forebrain induction
prechordal plate
44
formed between tip of notochord and oropharyngeal membrane
prechordal plate
45
contains a small region of tightly adherent ectoderm and endoderm cells
Oropharyngeal membrane
46
location of Oropharyngeal membrane
at cranial end
47
future opening of oral cavity
tightly adherent ectoderm and endoderm cells of Oropharyngeal membrane
48
the stage of development where the neural plate forms the neural tube
Neurulation
49
mark the beginning of the formation of the central nervous system
Neurulation
50
The first event in neurulation is
formation of the neural plate.
51
thickened area of cells in neurolation
neural plate
52
At what day does the notochord induces the ectodermal cells lying just cranial to the primitive node to differentiate into columnar neuroepithelial cells
19 days after fertilization
53
A process in which notochord induces the ectodermal cells lying just cranial to the primitive node to differentiate into columnar neuroepithelial cells
neural induction
54
What will the ectodermal cells differentiate into during neural induction
columnar neuroepithelial cells
55
Invaginating pre-notochordal cells move forward cranially in the midline until they reach the ___
prechordal plate
56
they intercalate in hypoblast creating 2 transient layers that form notochord plate
Pre-notochordal cells
57
what forms during intercalation of pre-notochordal cells
notochord plate
58
cells moving in the streak replace the hypoblast during neurolation
Endoderm cells
59
notochordal plate cells proliferate then detach from endoderm forming a solid cord of cells called
definitive notochord
60
this underlies neural tube
definitive notochord
61
Signaling center for inducing axial skeleton
definitive notochord
62
T/F, Notochord formation is a static process
false, dynamic
63
what forms first during notochord formation {cranial/caudal}
cranial end`
64
They extend cranially to the prechordal plate during notchord formation
Notochord and prenotochordal plate
65
area caudal to oropharyngeal membrane
prechordal plate
66
Notochord and prenotochordal plate extend cranially to the ___and to ___caudally
prechordal plate
| primitive pit
67
This temporarily connects amniotic and yolk sac cavities
neurenteric canal
68
formed from embryonic disc’s caudal end
Cloacal membrane
69
similar structure to oropharyngeal membrane
Cloacal membrane
70
Cloacal membrane contains {tightly/loosely} adherent ectoderm and endoderm cells with {no/rich} mesoderm
tightly
| No
71
Once cloacal membrane appears, the yolk sac’s {posterior/anterior} wall forms a small ___extending to connecting stalk
posterior
| diverticulum
72
What appears at 16th day of development during neurolation (2)
diverticulum, allantoenteric diverticulum, or allantois
73
aka allantosis
allantoenteric diverticulum
74
Lower vertebrates: ___as reservoir for excretion products of renal system
allantois
75
In Humans, allantois, may be involved in bladder development abnormalities. T/F
true
76
The neural plate forms at the ___of the embryo
cranial end
77
indicates the region of the eventual brain
cranial end of the neural plate
78
represents the eventual region of the spinal cord.
narrower caudal end
79
By the end of the ___week of development, the lateral edges of the neural plate become elevated, and fold to form the neural fold
third
80
the lateral edges of the neural plate become {elevated/depressed}, and fold to form the ___
elevated
| neural fold
81
The groove created by the folding of the neural plate is called
neural groove
82
at what level of somite does the two neural folds approach each other
4th level
83
Approximately ___after fertilization, the folds fuse together, and the neural plate transforms into the neural tube
25 days
84
it is the precursor to the central nervous system
neural tube
85
Fusion of the neural tube usually begins in the ___region
cervical
86
The openings that are formed at the cranial and caudal ends of the embryo are called
cranial and caudal neuropores
87
• During the closure of the neural tube, cells on the lateral side of the neural plate detach forming a new cell population, called
neural crest
88
migrate and displace the cells of the ectoderm to enter the underlying mesoderm
neural crest cells
89
neural crest cells contribute to the formation of (2)
peripheral nervous system,
formation of neurons and glial cells of the sympathetic, parasympathetic, and sensory nervous systems
90
Marks the end process of neurulation
complete fusion of neural tube
91
What are the body axes (3)
anterior posterior (A-P; craniocaudal),
dorso-ventral (D-V),
left-right (L-R)
92
T/F, Establishment of body axes occurs late in embryogenesis
false, early
93
Initiated during __stage with A-P and D-V axes specified prior to L-R
morula
94
T/F, A-P and D-V axes specified prior to L-R
true
95
A-P axis determined at what stage
blastocyst stage
96
Cells from cranial end of endoderm layer of bilaminar disc migrate towards what will become the head region to form the
anterior visceral endoderm (AVE)
97
At this bilaminar disc stage, cells from AVE express genes for head formation
anterior visceral endoderm (AVE)
98
AVE includes (2)
Transcription factors
Secretion factors
99
Transcription factors for AVE (3)
OTX2, LIM1, and HESX1
100
Secretion factors for ave (2)
cerberus and leftyl (members of the TGF-β family)
101
They inhibit nodal activity hence establishing cranial end of embryo
cerberus and leftyl
102
T/F, Absence of cerberus and leftyl at caudal end inhibits nodal expression to continue;
false, allows
103
T/F, Nodal expression will establish and maintains primitive streak
true
104
It upregulates genes responsible for formation of dorsal and ventral mesoderm and head and tail structures
NODAL
105
T/F, NODAL is member of TGF-alpha family
false, tgf-beta
106
This is secreted throughout embryonic disc
Bone morphogenetic protein 4 (BMP4)
107
combination in which mesoderm would be ventralized
BMP4 with FGF
108
T/F, The node is the organizer
true
109
Antagonistic genes of BMP4 (5)
```
Chordin
Noggin
Follistatin
Nodal
goosechoid
```
110
CHORDIN: activated by transcription factor __?
GOOSECOID
111
In BMP4 antagonists, cranial mesoderm is dorsalized into (3)
notochord, somites, and somitomeres
112
3 genes important for neural induction in the cranial region
notochord, somites, and somitomeres
113
responsible for initiating and maintaining primitive streak
Nodal
114
maintains node and later induces regional specificity in forebrain and midbrain areas
HNF-3β
115
Absence of HNF-3β will result to (2)
embryos fail to gastrulate properly
lack forebrain and midbrain structures
116
controls regulation of dorsal mesoderm formation
BRACHYURY (T) gene
117
BRACHYURY (T) gene is expressed in the ___ (3)
node,
notochord precursor cells,
and notochord
118
Responsible for cell migration through the primitive streak
BRACHYURY (T) gene
119
BRACHYURY (T) gene encodes a sequence-specific DNA-binding protein that functions as a
transcription factor
120
DNA-binding domain
T-box
121
__genes in the T-box family
>20
122
Absence of T-box would result in
caudal dysgenesis
123
embryonic axis shortening
caudal dysgenesis
124
In caudal dysgenesis, Degree of shortening depends on time which protein becomes excessive . T/F
false, deficient
125
Laterality or L-R sidedness also established in {early/late} development
early
126
T/F, Normally, many organs exhibit asymmetries
true
127
Organs that exhibit assymetries
• Heart, lungs, gut, spleen, stomach, liver, and others
128
Once primitive streak appears, cells of the node and primitive streak secrete __
FGF8
129
growth factor induces expression of NODAL
FGF8
130
T/F, NODAL expression often restricted to right side of embryo
false, left
131
Why is nodal expression often restricted to right side of embryo
due to serotonin (5-HT) accumulation on left side
132
These establishes midline and prevent NODAL expression from crossing over to the right side (3)
SONIC HEDGEHOG (SHH),
LEFTY1,
ZIC3
133
activates transcription factor MAD3 expression to the left side of primitive node
5-HT
134
From the left lateral plate, Nodal protein initiates signal cascade with LEFTY2 to upregulate ___
PITX2
135
Homeobox-containing transcription factor
PITX2
136
Master gene for left-sidedness establishment
PITX2
137
Promotes repeated expression in left side of heart, stomach, and gut primordial as they assume the normal asymmetrical body positions
PITX2
138
T/F, Genes for right-side regulation not as well defined
true
139
Transcription factor that is restricted to right lateral plate mesoderm
SNAIL
140
regulates effector genes for right side establishment
SNAIL
141
T/F Cascade initiated to the left involve cilia on cells in the node
true
142
establishes signaling gradient (2)
• gap junctions and small ion transport
143
create gradient of NODAL towards the left
cilia on cells in the node
