Ebook The science of stem cells: Part 2
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Ebook The science of stem cells: Part 2
9Cell Differentiation and GrowthThe previous chapters have covered the account of mammalian development from the generation of gametes to the formatio Ebook The science of stem cells: Part 2on of organ rudiments. Developmental biology textbooks often stop at this point, but here we shall continue and look at some selected examples of how organ rudiments become the functional tissues and organs of the body. All tissue types grow and expand during development, but most of those dealt wit Ebook The science of stem cells: Part 2h here do not have real stem cells which persist through adult life. Several bona fide stem cell systems are dealt with in Chapter 10. but in the presEbook The science of stem cells: Part 2
ent chapter the only tissue types which have stem cells are skeletal muscle and the central nervous system. Those of skeletal muscle are a population 9Cell Differentiation and GrowthThe previous chapters have covered the account of mammalian development from the generation of gametes to the formatio Ebook The science of stem cells: Part 2all stem cell populations in specific areas. Otherwise there are no true stem cells although some tissue types maintain slow cell turnover by division of their functional differentiated cells.Organs, Tissues and Cell TypesThe three concepts of “organ”, “tissue” and “cell type" are often confused, as Ebook The science of stem cells: Part 2 when speaking of “muscle" without specifying whether what is meant is the whole anatomical muscle or just the multinucleated myofibers within a musclEbook The science of stem cells: Part 2
e. An actual muscle contains many other tissues and cell types, including connective tissue, blood vessels, nerves and macrophages. Gene expression st9Cell Differentiation and GrowthThe previous chapters have covered the account of mammalian development from the generation of gametes to the formatio Ebook The science of stem cells: Part 2 expression repertoires. This means that the gene expression patterns of organs are dominated by the most abundant mRNAs from the most abundant cell types in the sample. Worse, these data are then used for various purposes by theoreticians who may not appreciate the limitations of the information ar Ebook The science of stem cells: Part 2ising from the complexity' of the initial samples. So it is really worthwhile to be clear about what is meant by organ, tissue or cell type in specifiEbook The science of stem cells: Part 2
c situations.An organ is a named part of the body familiar from gross anatomy. The stomach, the kidney, or the lungs are all organs. The skin is also 9Cell Differentiation and GrowthThe previous chapters have covered the account of mammalian development from the generation of gametes to the formatio Ebook The science of stem cells: Part 2h in turn usually contain multiple cell types.There is no clear definition of a “tissue" in the histological literature, but a tissue may usefully be regarded as the set of cell types originating from a single type of stem cell (or embryonic progenitor cell if the tissue in question does not have st Ebook The science of stem cells: Part 2em cells). Under this definition the small intestinal epithelium is a tissue. It is composed of multiple cell types, but they all come from one stem cEbook The science of stem cells: Part 2
ell population. The small intestine as an organ comprises also the connective tissue layers, the blood vessels, the lymphatics, the nerve supply, and 9Cell Differentiation and GrowthThe previous chapters have covered the account of mammalian development from the generation of gametes to the formatio Ebook The science of stem cells: Part 2 from one type of progenitor: the hepatoblast. The liver as an organ also contains an abundant vascular system and numerous cells of different lineages: the Kupffer cells and hepatic stellate cells. Histology textbooks often classify tissues into five general types: epithelia, connective tissues, ne Ebook The science of stem cells: Part 2rvous tissues, muscle and blood. The last three are dealt with later, in this chapter and in Chapter 10, but some preliminary’ remarks on the first twEbook The science of stem cells: Part 2
o are appropriate here.EpitheliaEpithelia (singular: epithelium) are sheets of cells which may consist of one or many layers (simple or stratified). T9Cell Differentiation and GrowthThe previous chapters have covered the account of mammalian development from the generation of gametes to the formatio Ebook The science of stem cells: Part 2mnarStratified squamousSimple tubular glandSimple acinar glandBranched acinar gland(b)specializationMicrofilament bundleBasement membrane --Tight junctionAdherens junction DesmosomeHemidesmosome(c)Reticular fibersGround substanceFibroblastPlasmaBlood vessel Adipocytes (fat cells) LymphocyteFigure 9. Ebook The science of stem cells: Part 21 (a) Various types of epithelium, (b) structure of a typicalcellElastic fiberCollagen fibers9Cell Differentiation and GrowthThe previous chapters have covered the account of mammalian development from the generation of gametes to the formatio9Cell Differentiation and GrowthThe previous chapters have covered the account of mammalian development from the generation of gametes to the formatioGọi ngay
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