Human evolution; how our outer skin works (Introduction)

by David Turell , Saturday, March 14, 2020, 22:30 (1505 days ago) @ dhw

It is a progression of inner cells finally migrating to the outside and forming a barrier:

https://www.sciencedaily.com/releases/2020/03/200313155327.htm

"Skin is our body's most ardent defender against pathogens and other external threats. Its outermost layer is maintained through a remarkable transformation in which skin cells swiftly convert into squames -- flat, dead cells that provide a tight seal between the living portion of the skin and the world outside.

"'Throughout our lifetime, squames are continually being shed from the skin surface and replaced by inner cells moving outward," says Elaine Fuchs, Rockefeller's Rebecca C. Lancefield Professor, whose lab recently shed new light onto this process. "We've identified the mechanism that allows skin cells to sense new changes in their environment and very quickly deploy instructions to drive squame formation."

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"The skin's epidermis consists of an inner layer of stem cells that periodically stop dividing and move outward, toward the body surface. As the cells transit through subsequent layers, they face the increasingly harsh extremes of our environment, like variations in temperature. In the very last step, as they approach the surface, the cells' nuclei and organelles are suddenly lost in the dramatic transformation into squames.

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"With this method, [skipped over above] the researchers were able to show that a protein called filaggrin, which is known to be mutated in some skin conditions, plays a key role in granule formation. "If filaggrin is not functioning properly, phase separation fails to occur, skin lacks keratohyalin granules, and the cells can no longer transform in response to environmental triggers," says Quiroz."

Comment: As this shows all processes in life are guided succession of planned events.