Explain what tissues and or cavities in the adult may be missing or abnormal in these individuals. Explain the developmental problem that causes the deficits in the first pharyngeal arch formation. First arch syndrome occurs because neural crest does not migrate into the first pharyngeal arch. Describe how gastrulation occurs in chick embryos. Give details of the cell movements that occur to create the three primary germ layers and molecules that are thought to be involved in organizing these cell movements during gastrulation.
Gastrulation occurs solely on the blastodisc.
The most anterior portion is Hensen's node. Precursor endodermal cells migrate separately into primitive stread downward first into the blastocoel and then mesoderm cells migrate second. Cells that migrate through Hensen's node form the notochord and gut. Choose one of the following questions to answer. You may continue your answer on the back of this page, if necessary.