What is the Pharyngeal apparatus?
During the development of the head and neck the three developmental layers come together to form the pharyngeal apparatus (also called branchial apparatus) in the embryo on either side of the neck from the area of the future ear on down. They begin to form from tissue migrating from the neural crest cells (ectoderm). They end up with three layers, the outer layer of ectoderm and the inner layer of endoderm have varying amounts of mesoderm between them. The pockets of mesoderm are called arches. The indentations into this structure, where the mesoderm has migrated away, on the external surface form the clefts and the spaces on the inner surface are the pouches. The membranes are the thin layer of endoderm and ectoderm that are right against each other because of the mesoderm migrating away. They are the membrane between a pouch and a cleft.
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