Magic embryology: developing an immune and blood systems (Introduction)

by David Turell @, Wednesday, October 09, 2019, 18:32 (1709 days ago) @ David Turell

Early stem cells are tracked in embryos to learn how the systems develop:

"In a world first, scientists have created the human developmental liver cell atlas that provides crucial insights into how the blood and immune systems develop in the foetus. It maps changes in the cellular landscape of the developing liver between the first and second trimesters of pregnancy, including how stem cells from the liver seed other tissues to support the high demand for oxygen needed for growth.


"Until now, it was unknown precisely how the blood and immune systems develop in humans—a process known as haematopoiesis. As adults, it is bone marrow that creates our blood and immune cells. But in early embryonic life, the yolk sac and liver play a major role in making blood and immune cells. These cells subsequently seed peripheral tissues such as skin, kidney and finally bone marrow.


"A developing foetus requires huge amounts of oxygen to fuel growth. The research discovered that during development, 'mother' haematopoietic stem cells stay in the liver. But as the liver alone cannot supply sufficient red blood cells, the next generation 'daughter' cells—known as progenitor cells—travel to other tissues. They mature in places such as the skin, where they develop into red blood cells to help meet the high demand for oxygen.

"Dr. Elisa Laurenti, a senior author from the Wellcome—MRC Cambridge Stem Cell Institute and the Department of Haematology at the University of Cambridge, said: "We knew that as adults age our immune system changes. This study shows how the liver's ability to make blood and immune cells changes in a very short space of time, even between seven and 17 weeks post-conception. If we can understand what makes the stem cells in the liver so good at making red blood cells, it will have important implications for regenerative medicine.'"

Comment: these early cells are following a planned outline of development. Embryology is the science of understanding how sex produces multicellular organisms. When life was single celled, splitting was a simple sort of reproduction. Having two individuals contribute genes requires that a design plan be set up for each new reproduction of an individual which is not different from the parents, but of course, it might produce some variability. That is a point Darwin used, the variability, but Darwin simply accepted sexual reproduction, and could not explain how a chance evolutionary process could create such a complex mechanism like embryology.It had to be designed.

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