The development of the branchial region in vertebrates is no less dependent on the cooperation of parts of different origin than is the mouth region. The leading part in the development of this area belongs to the endoderm. The endodermal cavity in this region, from its beginning, is distended in a transverse direction. In amphibians it is derived from the [...]
In this article we will discuss about:- 1. The Lungs in the Vertebrates 2. The Liver in Vertebrates 3. The Pancreas and Bursa Fabricii in Vertebrates. The Lungs in the Vertebrates: The lungs develop from a rudiment which is a pocket-like evagination of the endodermal epithelium on the ventral side of the alimentary canal, just posterior to the branchial region. [...]
The relation between the archenteron and the definitive alimentary canal is very different in vertebrates with complete cleavage from that in vertebrates with incomplete (meroblastic) cleavage. The Relation in Lower Vertebrates: The archenteron in Amphioxus is originally lined with presumptive endoderm, presumptive mesoderm, and presumptive notochordal cells. When the notochord and the mesoderm are segregated from the endoderm, the latter [...]