Peter Attia· MD
you have these two muscular walls one of them runs longitudinally so runs in the direction of the lumen and one runs orthogonal to that it runs circularly this is one of the things i remember from anatomy was that you have these things where if the circular inner layer contracts that shrinks the lumen and the longitudinal one as it contracts shortens it along its long axis and i think that's what permits this remarkable peristaltic rhythmic contraction of the gut