samenvatting H10: folding morphogenesis van Prof Zwijsen

H10: FOLDING MORPHOGENESIS
A.ZWIJSEN




Inhoudsopgave
10.1 BECOMING A SHRIMP-SHAPED EMBRYO...........................................................2
10.1.1 FROM FLAT DISC TO SHRIMP-SHAPED CHICK EMBRYO..................................................................2
10.1.2 FROM CUP-SHAPED TO SHRIMP-SHAPED MOUSE EMBRYO.............................................................3
10.1.3 FROM FLAT DISC TO SHRIMP-SHAPED HUMAN EMBRYO................................................................3

10.2 VENTRO-LATERAL FOLDING MORPHOGENESIS (VFM)........................................4
10.2.1 VENTRO-LATERAL FOLDING MORPHOGENESIS IN MOUSE..............................................................4
10.2.1.1 gut internalization and body wall closure................................................................7
10.2.1.2 ventral folding + axial rotation (in the mouse)........................................................8
10.2.1.3 endoderm becomes regionalized............................................................................9
10.2.1.4 regional specification of gut endoderm and splanchnic mesoderm.........................9
10.2.1.5 looping morphogenesis of midgut.........................................................................11
10.2.2 VENTRO-LATERAL FOLDING MORPHOGENESIS IN HUMAN............................................................11
10.2.2.1 transforming the neural plate into a tube..............................................................11
10.2.2.2 ventro-lateral folding............................................................................................. 13
10.2.2.3 intra-embryonic coelomic cavities.........................................................................14
10.3 DRIVERS OF TISSUE MORPHOGENESIS...........................................................15
10.4 HUMAN FOLDING DISORDERS........................................................................17
10.4.1 GASTROSCHIZIS................................................................................................................ 17
10.4.2 HERNIA DIAPHRAGMATICA................................................................................................... 17




Goals:

 Comprehension of concepts of ventrolateral folding morphogenesis
 Understanding how heart and gut tubes are formed and internalized
 Understanding how the body cavities are established
 Insight in body wall closure defects

Lets revise:

Anterior = top and Posterior = bottom

The 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

1

,2). The different types of mesoderm that were formed at PS will migrate along these lines on
picture 3.



The blue cup is the ectoderm (epiblast)

As the primitive streaks lengthens there is
more and more mesoderm formed that
migrates away

The node is the organizer where the mesoderm
will develop on the midline.

Allantois is arrived from extra embryonic mesoderm. It needs to diffuse to the placenta to
connect with the blood circulation.



10.1 BECOMING A SHRIMP-SHAPED EMBRYO

Bovenste lijn: gastrula stage (development of the CZS)




10.1.1 FROM FLAT DISC TO SHRIMP-
SHAPED CHICK EMBRYO

It’s a dorsal view:

A. Is the endodermal side (ectodermal side is behind the screen).
Primitive streak: where gastrulation will happen. Dorsal ectoderm cells will start to
delaminate and become mesoderm.
B. Streak becomes shorter  formation of notochord
C. Neural ectoderm starts to form anterior from the node  neural plate  neural fold 
neural tube.
Behind the screen is the notochord (organizer that induces the neural plate to develop
into a tube)
D. Formation of somites from a to p from presomatic mesoderm
E. Neural tube extends while somites are formed  brain vesicles start to get shaped

later: head starts to turn  heart starts to pop out  complex folding




2

, Primitive streak: is a scratch where the
ectoderm cells come together -> undergo
EMT

The length of the streak reaches more
than half of the embryo.

The primitive streak regresses while
notochord lengthens.




10.1.2 FROM CUP-SHAPED TO SHRIMP-SHAPED MOUSE EMBRYO



Ts11: is a cup shape with left the anterior and right the posterior side. We
know this because we see the allantois on the right. The allantois will grow
out and later become the umbilical cord, it will fuse with the chorion which
is on top of the embryo.

Ts12: the dark shade (canal (kanaal)) is the fore gut entrance. The sides of
the cup shape embryo become very thin. In the bend you can also see
laterally the somites. Embryo is still on his belly and his eyes look away from the tail.

Ts13: if the embryo will have eyes they would look away from
the tail. Somites starts to develop. Endoderm is at the outside
of embryo. Axial rotation happens here. Embryo turns.

Ts14: Side of embryo is now located at the inner side. Dorsal
side (ectoderm) is on the outside. The embryo looks at its
future tail region. This process is important to internalize the
gut. Shrimp-like shape.




10.1.3 FROM FLAT DISC TO SHRIMP-SHAPED HUMAN
EMBRYO

The human embryo is more circular.
3