10. Folding Morphogenesis
Goals
Table of contents
How become tri-layer embryos ‘shrimp’-like?
We start at gastrulation, look at chicken embryo. Why do we like to use the chicken embryo?
Relatively big embryo, easy to manipulate, good surrogate for human embryos as both human and
chick develop in a flat disk whereas the mouse will develop into a cup shape.
anterior = top
posterior = bottom
embryo is kind of oval disk. Midline structure at posterior side is the primitive streak (PS). The round
structure anterior to the PS is the Hensen’s node (which is an organizer). From the node and PS
different types of mesoderm will develop, in the node notochord will form (the axial mesoderm)
which migrate on the midline towards anterior. From the primitive streak different classes of
mesoderm will form (see picture 2). The different types of mesoderm that were formed at PS will
migrate along these lines on picture 3.
Blue layer = epiblast, which will become the ectoderm. The mesoderm will migrate behind the screen
but still above the endoderm. Look at cross section.
1
, Gastrulation in the mouse embryo, cup shape. The thick
blue layer is the epiblast. At the posterior side the
mesoderm will develop at the PS. At first the PS is short,
it will elongate. When the PS gets at its longest the node
will be formed and in the node axial mesoderm, or
notochord will be formed, which will develop on the
midline. Elsewhere on the PS different types of
mesoderm will be formed and will migrate in between
the ecto- and endoderm, and will migrate more
anteriorly.
How does it acquire this shrimp like kind of shape?
From tri-laminar to shrimp? In which
the gastro-intestinal system has
become internalized, the neural tube
has been closed.
Question of today:
How do we go from
a flat disk to a
shrimp?
DORSAL view, because we can see neural
groove and tube developing on top of
a. Flat disk
b. PS already regressing
c. Regressing even more More tissues are being
d. And more formed anterior to the PS
e. And more
Alternative way of looking at it, using
EM. Anterior to the node you can find
the neural plate (np), where behind the
screen the notochord is present.
The PS forms at its longest the node and then starts to
regress. The anterior part will expand faster than the
posterior part. This gives the impression that the PS
shrinks but it’s more the anterior part that really
proliferates faster.
2
Goals
Table of contents
How become tri-layer embryos ‘shrimp’-like?
We start at gastrulation, look at chicken embryo. Why do we like to use the chicken embryo?
Relatively big embryo, easy to manipulate, good surrogate for human embryos as both human and
chick develop in a flat disk whereas the mouse will develop into a cup shape.
anterior = top
posterior = bottom
embryo is kind of oval disk. Midline structure at posterior side is the primitive streak (PS). The round
structure anterior to the PS is the Hensen’s node (which is an organizer). From the node and PS
different types of mesoderm will develop, in the node notochord will form (the axial mesoderm)
which migrate on the midline towards anterior. From the primitive streak different classes of
mesoderm will form (see picture 2). The different types of mesoderm that were formed at PS will
migrate along these lines on picture 3.
Blue layer = epiblast, which will become the ectoderm. The mesoderm will migrate behind the screen
but still above the endoderm. Look at cross section.
1
, Gastrulation in the mouse embryo, cup shape. The thick
blue layer is the epiblast. At the posterior side the
mesoderm will develop at the PS. At first the PS is short,
it will elongate. When the PS gets at its longest the node
will be formed and in the node axial mesoderm, or
notochord will be formed, which will develop on the
midline. Elsewhere on the PS different types of
mesoderm will be formed and will migrate in between
the ecto- and endoderm, and will migrate more
anteriorly.
How does it acquire this shrimp like kind of shape?
From tri-laminar to shrimp? In which
the gastro-intestinal system has
become internalized, the neural tube
has been closed.
Question of today:
How do we go from
a flat disk to a
shrimp?
DORSAL view, because we can see neural
groove and tube developing on top of
a. Flat disk
b. PS already regressing
c. Regressing even more More tissues are being
d. And more formed anterior to the PS
e. And more
Alternative way of looking at it, using
EM. Anterior to the node you can find
the neural plate (np), where behind the
screen the notochord is present.
The PS forms at its longest the node and then starts to
regress. The anterior part will expand faster than the
posterior part. This gives the impression that the PS
shrinks but it’s more the anterior part that really
proliferates faster.
2
