18. Early Embryonic Development - The Fate of the Mesoderm Flashcards
What has happened by the end of week 3 in early embryonic development?
The embryo has gastrulated and the bilaminar disk is converted to a trilaminar disk. The axes have been set and the three germ layers have developed: ectoderm, mesoderm and endoderm.
What is the objective of the mesoderm?
Notochord formation for neurulation, organisation of the mesoderm into somites, intermediate and lateral plate mesoderm.
What is the objective of segmentation?
To form dermatomes and myotomes.
What is the notochord responsible for?
Releasing signals to surrounding ectoderm.
What are the two parts of neurulation?
Notochord - driven induction of ectoderm to form the nervous system.
Neural plate - folds to develop the brain and spinal cord from the neural tube.
Where is the notochord found?
Between the ectoderm and endoderm.
How does neurectoderm form?
The notochord directs conversion of overlying ectoderm to neurectoderm.
How is the neural tube formed?
Cells at the edges of the neural plate so they rise up and curl round to meet each other and form the tube.
What is the paraxial mesoderm?
The mesoderm found either side of the axis.
What is the intermediate mesoderm?
The mesoderm found inbetween the axis and the edge.
What is the somatic mesoderm?
The mesoderm that goes on to give the skeletal muscle and is to do with body and body structures.
What is the splanchnic mesoderm?
The mesoderm to do with viscera/ organs, e.g. intestines.
What is the intraembryonic coelom?
The space inside the embryo (new cavity in gastrulation).
What are somites?
The organisation of paraxial mesoderm into segments.
When does the first somite appear in embryonic development?
At day 20.