When does gastrulation occur?
At the end of the second week of gestation
What happen at the end of week three of gestation?
-three distinct embryonic germ layers are formed:
+ectoderm
+mesoderm
+endoderm
Cells entering the ICM earliest express ________ and are destined to become __________ cells.
- Nanog
- epiblast
Cells entering ICM later express ________ and are destined to become. ________ cells.
- Gata 6
- hypoblast
What can induce the expression of Gata 6?
-FGF-6 secretion from earlier cells
Define coelom.
Mesodermal you lined cavity
What is the two germ layer stage? What are these layers?
-initial stage of the embryo consisting of two cell layers derived from the ICM
+epiblast
+hypoblast
What is the primitive streak possibly induced by?
- TGF-beta
- Wnt
What are bottle cells?
- cells associated with the primitive streak
- transforming cells are freed from the basal lamina and lose E-cadherin
- turn into mesenchymal cells and will become part of the mesodermal germal layer
What structure is lined with only ectoderm and endoderm?
-oropharyngeal membrane
Epithelial mesenchymal cell transformation is correlated with expression of what transcription factor?
-snail
Is the amnion a coelom?
NO, lined with ectoderm not mesoderm
Review slide 27
Ok!
What structures express E-cadherins and N-CAMs?
-prior or induction, ectoderm expresses both E and N
- after neural tube induction, neural tube ectoderm only expresses N-CAM and N-cadherin
- after neural tube induction, overlying ectoderm only expresses E-cadherin
