On the growth and form of the gut

Abstract

Summary The developing vertebrate gut tube forms a reproducible looped pattern as it grows into the body cavity. Here we use developmental experiments to eliminate alternative models and show that gut looping morphogenesis is driven by the homogeneous and isotropic forces that arise from the relative growth between the gut tube and the anchoring dorsal mesenteric sheet, tissues that grow at different rates. A simple physical mimic, using a differentially strained composite of a pliable rubber tube and a soft latex sheet is consistent with this mechanism and produces similar patterns. We devise a mathematical theory and a computational model for the number, size and shape of intestinal loops based solely on the measurable geometry, elasticity and relative growth of the tissues. The predictions of our theory are quantitatively consistent with observations of intestinal loops at different stages of development in the chick embryo. Our model also accounts for the qualitative and quantitative variation in the distinct gut looping patterns seen in a variety of species including the quail, finch and mouse illuminating how the simple macroscopic mechanics of differential growth drives the morphology of the developing gut.

Creases on the interface between two soft materials

“…They exist in composite materials 1 , geological strata 2,3 , electronic devices 4 , biological tissues 5,6 and soft actuators 7 . In many cases, stresses arise due to differences in thermal expansion [8][9][10] , chemical reactions 11 , growth 5,12 , swelling 13 , or mechanical pre-strains 14 . Such mismatches may cause buckling instabilities 1, 10,15,16 , which can reduce the strength of structures 1,10,15,16 and lead to debonding of the interfaces 8,9,17 .…”

Extreme mechanics: Buckling down

“…These researchers have been inspired, in part, by advances in geometry and nonlinear mathematics that have allowed them to progress where their forebears could not. They have already, for example, devised a theory for why cabbage leaves and torn plastic rubbish bags ripple 1 ; calculated the patterns of wrinkles in fabric and crumples in paper 2 ; and accounted for the way coils and loops develop in the guts of vertebrate embryos 3 .…”

Emergent perversions in the buckling of heterogeneous elastic strips

“…The strip-like geometry does not impose a constraint on the allowed number of perversions. Multiple perversions have been found in animal guts (18) and in the bistrip model (4). The specific number of perversions in a helical strip is determined by several factors, such as the materials property and the external constraints (4,26).…”

“…In contrast to domain walls in prototype spin systems, perversions embedded in both natural (6, 17) and artificial (4) helical systems have the unique freedom to wind around themselves in response to mechanical or geometric constraints. This salient feature of perversions accounts for several important observations, including the generation of more helices by a self-winding single perversion (6) and formation of the ripple patterns extensively found in animal guts and leaf edges through multiple perversions (18,19). Recent studies have further revealed that the perversion in the cucumber tendril, with its variable local stiffness, can unexpectedly overwind under tension rather than unwind (20).…”