Morphogenesis

Question 1

Different cell layers are separated during gastrulation because of:

Answer 1

• Cell adhesiveness: tendency to stick to one another = key mechanism cell shape & migration
• Cell shape
• Cell migration

Question 2

Differential adhesion hypothesis cells from different germ layers do not mix due to surface tension and interfacial tensions → explains liquid- like tissue dynamics,
This can be shown in several invitro experiments:

Answer 2

• Isolate 2 pieces of endoderm from amphibian blastula and mix them → formation of a smooth sphere in culture
• Dissociate cells from two different tissues (mesoderm and ectoderm) at early gastrula → mix → let cells reaggregate
  Result: two different tissues are reformed → mesodermal cells on the outer surface,
  surrounding a mass of epidermal cells (epidermal cells are more adhesive, so they
  stick together stronger than mesodermal cells)

Question 3

Cell adhesion molecules, three classes:

Answer 3

• Cell-cell adhesion
  o Cadherins
  o Immunoglobulin superfamily
• Cell-matrix adhesion
  o Integrins

Question 4

cytoskeletons (3)

Answer 4

-intermediate filament
-microtubules
-actin filaments

Question 5

main movement in gastrulation (3)

Answer 5

• Involution
• Convergent extension
• Epiboly