Trilaminar Germ Disc Flashcards
It is the process that establishes all 💡three germ layers (ectoderm, mesoderm, and endoderm) in the embryo.
GASTRULATION
It is the 💡most characteristic event occurring during the 💡third week of gestation.
GASTRULATION
Gastrulation begins with formation of the __ on the surface of the epiblast.
It is a place where cells of the epiblast migrate
Primitive streak
Initially, the streak is vaguely defined, but in a __, it is clearly visible as a narrow groove with slightly bulging regions on either side.
15- to 16-day embryo
It is the 💡cephalic end of the primitive streak.
Consists of a slightly elevated area surrounding the small 💡primitive pit
Primitive node
This growth factor controls 💡cell migration a by 💡 down regulating E-cadherin and controls 💡 cell specification into the mesoderm by regulating 💡 BRACHYURY (T) expression.
It induces the expression of 💡NODAL
Fibroblast growth factor 8 (FGF8)
It is a protein that normally 💡binds epiblast cells together.
E-cadherin
Once the cells have invaginated, some 💡displace the hypoblast, creating the embryonic __.
Endoderm
Once the cells have invaginated, others come to 💡lie between the epiblast and 💡newly created endoderm to form __.
Mesoderm
Cells remaining in the epiblast then form __.
Ectoderm
It is the source of all three germ layers through the process of gastrulation.
Epiblast
It is important for induction of the 💡forebrain.
It is an area just 💡caudal to the oropharyngeal membrane.
It is formed by the 💡mesoderm cells.
Prechordal plate
It consists of a small región of 💡tightly adherent ectoderm and endoderm cells that represents the future opening of the 💡oral cavity.
Oropharyngeal membrane
These cells invaginating in the 💡primitive node move forward cranially in the midline until they reach the 💡prechordal plate
Prenotochordal cells
These 💡prenotochordal cells become intercalated in the 💡hypoblast so that for a short time, the midline of the embryo consists of two cell layers that form the __.
Notochordal plate
These are 💡solid cord of cells formed when 💡cells of the notochordal plate proliferate and detach from the endoderm.
It underlies the 💡neural tube and is a 💡signaling center for inducing the 💡axial skeleton.
Definitive notochord
Because elongation of the notochord is a dynamic process, the __ forms first, and __ are added as the primitive streak assiunes a more caudal position.
Cranial end
Caudal regions
It 💡temporarily connects the amniotic and yolk sac cavities at the point where the pit forms an indentation in the epiblast.
Neurenteric canal
It is formed at the 💡caudal end of the embryonic disc
CSimilar in structure to the oropharyngeal membrane.
It consists of 💡tightly adherent ectoderm and endoderm cells with 💡no intervening mesoderm.
Cloacal membrane
It appears around the 💡16th day of development when the 💡cloacal membrane appears, the 💡posterior wall of the yolk sac forms a 💡small diverticulum that extends into the connecting stalk.
Allantoenteric diverticulum or Allantois
Establishment of the __, occurs early in embryogenesis and is probably initiated dur- ing the mórula stage of development with the A-P and D-V axes specified prior to the L-R.
Body axes, anterior- posterior (A-P; craniocaudal), dorso-ventral(D-V), and left-right (L-R)
At this bilaminar disc stage, cells in the __ express genes essential for head formation.
Anterior visceral endoderm (AVE)
These are genes essential for head formation;
Transcription factors:
OTX2
LIMl
HESXl
Secreted factors:
Cerberus and leftyl (members of the TGF-beta family)
These are secreted factors gene which 💡inhibit nodal activity.
Cerberus and Leftyl
