Gastrulation and neurulation Flashcards
When does gastrulation begin?
beginning of week 3
What has happend by the end of week 2?
- bi-laminar disc is separated into epiblast and hypoblast
- yolk sac id definitive
- amniotic cavity is present
What are the raised groove and pit on the epiblast called?
primitive streak
primitive node
What happens at the primitive streak and node?
epiblast cells stream into the embryo along the primitive streak and node and the trilaminar disc is established
How is the endoderm created?
migrating epiblast cells replace hypoblast cells
How is the mesoderm created?
epiblast cells spread between the two layers
What is the notochord?
a specialised signalling mesoderm structure formed between the two layers in front of the node
What is the role of the primitive node/notochord in neurulation?
organises the dorsal structures
What happens at day 19+?
the midline groove becomes apparent
What happens on day 22?
the cervical region fuses to form the neural tube
What happens if the neural tube fails to close?
anencephaly - the absence of a major part of the brain
What are neural crest cells?
specialised cells that migrate away from the neural tube epithelium
What can defective neural crest development result in?
Waardenburg’s syndrome
Treacher Collins Syndrome
What are the 4 types of mesoderm formed?
intermediate
paraxial
lateral plate
midline
What happens to paraxial mesoderm?
becomes segmented to become somites
