Gastrulation rearranges a blastula into a triploblastic gastrula with three germ layers - ectoderm, mesoderm and endoderm. These germ layers then differentiate into various tissues and organs through the process of organogenesis. Patterning and morphogenesis in animal development involves changes in cell shape, position and adhesion regulated by the cytoskeleton, extracellular matrix, cell adhesion molecules and growth factors.
2. Gastrulation rearranges the embryo into a
triploblastic gastrula.
Gastrulation rearranges the
blastula to form a three-layered
embryo with a primitive gut
Primary Germ Layers
Ectoderm
Endoderm
Mesoderm
11. • The amniote embryo is the solution to
reproduction in a dry environment.
Amniote embryos develop in a fluid-
filled sac within a shell or uterus
chorion
amnion
embryo
allantois
yolk sac
Extraembryonic membrane
Fetal portion of placenta
Maternal portion of placenta
reptile & bird mammal
12. • The four extraembryonic membranes are
the yolk sac, amnion, chorion, and
allantois.
–Cells of the yolk sac digest yolk
providing nutrients to the embryo.
–The amnion encloses the embryo in a
fluid-filled amniotic sac which protects
the embryo from drying out.
–The chorion cushions the embryo
against mechanical shocks.
–The allantois functions as a disposal sac
for uric acid.
13. Mammalian Development.
–Recall:
• The egg and zygote do not exhibit any
obvious polarity.
• Holoblastic cleavage occurs in the zygote.
–Gastrulation and organogenesis follows a
pattern similar to that seen in birds and
reptiles.
20. • Changes in
cell
shape usually
involves
reorganization
of the
cytoskeleton.
Morphogenesis in animals involves
specific changes in cell shape, position,
and adhesion
21. • The cytoskeleton is also involved in cell
movement.
– Cell crawling is involved in convergent
extension.
• The movements of convergent extension probably
involves the extracellular matrix (ECM).
• ECM fibers may direct cell movement.
• Some ECM substances, such a
fibronectins, help cells move by
providing anchorage for crawling.
• Other ECM substances may inhibit
movement in certain directions.
33. BMP in neural tube
formation
1. Inhibition of BMP
signaling
2. At end of neurulation the
lateral edges of the
neural plate fuse
3. They segregate from the
non-neural epithelia to
form a neural tube
4. Roof plate of neural tube
now produces BMP. BMP
stimulates neural crest
cell formation