Embryonic Induction - Lecture notes 1-3 PDF

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Embryonic induction biotechnology notes...

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EMBRYONIC INDUCTION Definition. Embryonic induction describes the embryonic process in which one group of cells, the inducing tissue, directs the development of another group of cells, the responding tissue. Induction directs the development of various tissues and organs in most animal embryos; for example, the eye lens and the heart. Embryonic induction is an embryonic process. In this process, one group of cells induces the development of another group of cells. Likewise, different inducing tissues induce the development of various tissues and organs during the embryonic development in most animal embryos. In short, in embryonic induction, the presence of one tissue influences the development of other tissues in the very young embryo. Therefore, the absence of an inducing tissue results in improper development of the other tissues. There are two types of embryonic induction as primary and secondary embryonic induction. Primary embryonic induction refers to the events taking place during the early embryogenesis. Secondary embryonic induction refers to the tissue interactions that result in various cell types. Primary embryonic induction is the first induction event that takes place during early embryogenesis. Firstly, tissues interact to generate the neural tube. Neural tube eventually forms the central nervous system. The cells of the neural crest induce the surface ectoderm cells in order to proliferate and invaginate to form the neural tube. Primary embryonic induction is the first induction event that takes place during early embryogenesis. Firstly, tissues interact to generate the neural tube.......The cells of the neural crest induce the surface ectoderm cells in order to proliferate and invaginate to form the neural tube.

What is Secondary Embryonic Induction? Secondary embryonic induction is the development of various tissues and organs in animal embryos. Therefore, in secondary induction, tissues interact in order to govern cell differentiation and morphogenesis during embryonic development. Many cell types originate as a result of secondary induction. Development of eye and ear is an example of secondary embryonic induction. Moreover, as a result of secondary embryonic induction, tooth, hair, lens and many organs are formed. Secondary embryonic induction starts once the basic embryonic

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plan has been established. A chain of secondary induction processes takes place differentiating many specialized cell types.

What are the Similarities Between Primary and Secondary Embryonic Induction?  

Both, primary and secondary embryonic induction play an important role in the development of tissues and organs in most animal embryos. The molecular nature of “primary” and “secondary” inductions is similar.

What is the Difference Between Primary and Secondary Embryonic Induction? Primary embryonic induction is the tissue interactions in early embryogenesis that generate the neural tube. Secondary embryonic induction is the embryonic induction that directs the development of various tissues and organs in most animal embryos. So, this is the key difference between primary and secondary embryonic induction.

Secondary Induction Many other cell types originate as a result of inductive interaction throughout development of the organism; this is secondary induction. Inductive interactions have been classified as either instructive or permissive. In an instructive interaction, the inducing tissue apparently gives precise information to commit cells to a new pathway of development. Using the chick, Cairns and Saunders (1954) transplanted mesoderm from different regions of the

leg or wing into foreign regions and showed that the overlying ectoderm developed according to the origin of the mesoderm. If a piece of thigh mesoderm is grafted under the ectoderm of the wing, the developing wing ectoderm will form thigh feathers above the grafted mesoderm. Such an interaction presumes that the responding tissue is relatively undetermined. Besides having a definite normal fate, called prospective significance, the parts of the embryo have the ability to develop into other parts, under experimental conditions. This ability of parts of an early embryo to develop into more than one type of tissue is called prospective potency. The narrowing of prospective potencies, which fixes the fate of the embryonic tissues, is called determination. After determination has occurred in a tissue that tissue is said to be determined. It now has a more narrow prospective potency. Instead of a single instructive event precipitating the formation of the lens from the head ectoderm, recent work examining the induction of the amphibian lens suggests that induction of this tissue is a multi-step process, and there appears to be a series of inductive events that progressively bias the head ectoderm to form lens. In permissive interactions, responding cells are already determined and poised to differentiate; they simply require a signal from the inducing tissue to allow them to express their potential. The pancreas is a good example. It develops as an outgrowth of the gut, but its development requires a contribution from the mesoderm. If pancreatic mesoderm and endoderm are separated and cultured separately in a 9-day mouse embryo, development ceases. If they are recombined in culture, the endoderm does differentiate into normal exocrine and endocrine cells of the pancreas. Rutter and his colleagues (1964) found that substituting a different type of mesenchyme, from the salivary gland, would cause pancreatic endoderm differentiation. This endoderm differentiation was also observed using somites (which normally produce muscle and cartilage cells) and young pureed embryos (embryo extract). Therefore, at the time the pancreatic endoderm is observable, it is apparently already determined to the extent that a relatively non- specific cue will complete the differentiation process.

Summary – Primary vs Secondary Embryonic Induction During embryogenesis, the process of one group of cells influences or induces the direction of differentiation of the neighbouring group of cells is known as embryonic induction. It is the most important mechanism in vertebrate development. When the chordamesoderm contacts the dorsal ectoderm, induction of neural ectoderm takes place. It is known as primary embryonic induction. In primary embryonic induction, the surface ectoderm cells develop into the neural tube. Neural tube eventually forms the central nervous system. Secondary embryonic induction is the development of many tissues and organs due to embryonic induction. Thus, this summarizes the difference between primary and secondary embryonic induction....