Human Development Lecture 7 – Placenta formation
How do cells know where to go?
First cells look very similarly if you wait then they form different
structures
Cells fate (het lot van de cel) develops progressively.
It depends on sets of transcription factors.
Determines cell fate;
Position of cells
Transcription factors
• Oct4 & Nanog; expressed in morula stage. When they are expressed
trophoblast disappear and ICM maintained.
Function is ICM formation.
• Cdx2 & Eomes; expressed in throphoblast.
Function is downregulation of Oct4 and Nanog, so these are expressed in
morula stage → spread through whole cell. There is no
differentiation between trophoblast and ICM.
Making the placenta
Amniotic sac; water sac; embryo develops in this
Extraembryonic mesoderm; around yolk sac and amniotic sac. It is
the major site for hematopoiesis. There is a formation of blood
islands. Venous and arterial vessels.
Chorion; cytotrophoblast + extraembryonic
mesoderm
Yolk sac; blood cell formation
Amnion; cushion for the embryo or fetus
Allantois; urinary bladder
Chorion (vili); formation of placenta
Blood forming cells over development;
Yolk sac
Ciruclation; Aorta, gonad, mesonephros
(structure similary to kidney of adult) (=AGM), placenta
Birth; fetal liver, bone marrow (adult)
How do cells know where to go?
First cells look very similarly if you wait then they form different
structures
Cells fate (het lot van de cel) develops progressively.
It depends on sets of transcription factors.
Determines cell fate;
Position of cells
Transcription factors
• Oct4 & Nanog; expressed in morula stage. When they are expressed
trophoblast disappear and ICM maintained.
Function is ICM formation.
• Cdx2 & Eomes; expressed in throphoblast.
Function is downregulation of Oct4 and Nanog, so these are expressed in
morula stage → spread through whole cell. There is no
differentiation between trophoblast and ICM.
Making the placenta
Amniotic sac; water sac; embryo develops in this
Extraembryonic mesoderm; around yolk sac and amniotic sac. It is
the major site for hematopoiesis. There is a formation of blood
islands. Venous and arterial vessels.
Chorion; cytotrophoblast + extraembryonic
mesoderm
Yolk sac; blood cell formation
Amnion; cushion for the embryo or fetus
Allantois; urinary bladder
Chorion (vili); formation of placenta
Blood forming cells over development;
Yolk sac
Ciruclation; Aorta, gonad, mesonephros
(structure similary to kidney of adult) (=AGM), placenta
Birth; fetal liver, bone marrow (adult)
