gastrulation in mammals

1. Gastrulation in mammals
Ritu sheoran
Roll –no 933
BSC zoology hons .

2. Gastrulation in mammals:-
 Gastrulation is a process involving a complex sereies of
cell shape changes and cell movements that occurs in
blastula.
 It establishes the basic body plan and creates the three
primary germ layers.
 Ectoderm-exterior
 Mesoderm-middle
 Endoderm-inner

3.  Ectoderm-epidermis of skin,nervous system,sense organs.
 Mesoderm-skeleton,muscles,blood
vessels,heart,blood,gonads,kidneys,dermis of skin.
 Endoderm-lining of digestive and respiratory
tracts,liver,pancreas,thymus,thyroid.
 Cells move during gastrulation using a variety of cell
shape changes.
 Cells that are tightly attached to each other via junctions
will move as cell sheets.
 Invagination- cell sheet dents inward.
 Involution-cell sheet rolls inward.
 Delamination-cell sheet splits in two.
 Ingression-cells break away from cell sheet and migrate as
individual cells.

4. Gastrulation patterns in mammals:-
 The gastrular movements that is the formation of primitive
streak and groove are similar to that of birds.
 Embryo develops from inner cell mass.
 The cell movements through give rise three germ layers.
 The inner cell mass,or embryoblast differentiates into lower
hypoplastic and upper epiblast forming a bilaminar disc.
 The cell of hypoblast then spread around the blastocyst cavity as
extraemryonic endoderm forming a yolk sac,which is only a fluid
filled cavity without yolk.
 The underlying hypoblast cells are cuboidal but become
columnar one side to form the prechordal plate.

5. Gastrulation in mammals:-

6. Extraemryonic membrane:-
 Nourish and protect the developing embryo.
 These membrane are formed from embrynoic cell.
 Formation of fetal membranes , a characteristic feature
of amniotes ,begin the onset of gastrulation as there is
immediate requirement of food by the growing embryo .

7.  Amnion=encloses amniotic fluid.
 Chorion-contributes to the placenta in mammals.
 Yolk –sac =found in mammals but it is not nutritive.
 Allantois- in mammals ,it contributes blood vessels to the
developing umbilical cord.
 When the cell mass is isolated and grown under certain
conditions,the cells remain undifferentiated and divide in
culture .They are called embryonic stem cells ,which are
exploited for therapeutic use.

8. Thank you