which are the experiments that prove the thymus comes from only one germ layer and is...

which are the experiments that prove the thymus comes from only one germ layer and is not derived from ectoderm and endoderm?

Expert Solution

Thymus is a bilobed primary organ essential for the generation of functional T cells and is located on the top of the heart in the central compartment of the thoracic cavity. The development of thymus is associated with small endocrine glands in the neck known as parathyroid glands that are responsible for maintaining calcium homeostasis. The embryonic development of lymphocytic components of the thymus and parathyroid glands occur from single primordia. The epithelial cells instruct the mesenchyme to participate in the thymus development. This can be understood by an experiment in which mice embryonic thymus lobes were dissociated into the epithelial primordium and capsule of mesenchymal. These two were then cultured alone or combined with mesenchyme capsule. It was observed that epithelial primordium fails to develop in the absence of mesenchymal cells. So this experiment clearly reveals the significance of epithelial-mesenchymal interactions in the morphogenesis and growth of thymus. Histological and histochemical experiments are done for understanding how the epithelial portion of the thymus derived entirely from pharyngeal pouch endoderm. Further two chick quail chimera studies have shown that mesenchymal capsules and the pericytes in the thymus are derived from neural crest cells. Experiments done on medulla consisting of clonal clusters of cells have shown that progenitor cell mechanisms are essential for thymic epithelial cells (TECs) differentiation. Labeling of the surface ectoderm coupled with whole embryo culture have shown to demonstrate that ectodermal cells do not contribute physically to the development thymus. Gene expression and genetic studies in mice have shown the involvement of many transcription factors and signaling pathways that play essential roles in thymus organogenesis.

gladiator answered 2 years ago

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