In order to breathe in, we must
flatten the dome-shaped diaphragm; to breath out, we let it relax again. The
diaphragm delivers oxygen to us a dozen times or more each minute, a
half-billion times during an 80-year life.
Before the evolution of a diaphragm,
our reptilelike ancestors probably breathed the way many reptiles do today.
They used a jacket of muscles to squeeze the rib cage.
Scientists
suspect that the diaphragm evolved through some change in the way mammal
embryos develop: Mutations caused certain embryonic cells to grow into an
entirely new muscle. Dr. Kardon and other researchers are trying to understand
that shift and why the muscle sometimes fails to develop, with catastrophic
consequences.
Original Article:http://www.nytimes.com/2015/04/07/science/behind-each-breath-an-underappreciated-muscle-the-diaphragm.html?rref=collection%2Fsectioncollection%2Fscience&action=click&contentCollection=science®ion=stream&module=stream_unit&version=search&contentPlacement=10&pgtype=sectionfront
