A Computational Model for Gut Looping

In chick embryos, a series of complex invaginations involving the three germ layers (endoderm, ectoderm, and mesoderm) lead to the formation of the primitive gut tube. This process normally occurs during the third day of development, at the end of which the gut appears as an open cylindrical tube (Fig.1A). By the end of the fourth day, the tube is closed except in the middle section, which is connected to the yolk sac (Fig. 1B). The gut at this stage is typically divided into three sections: the foregut, midgut, and hindgut. Now starts the process of gut looping that transforms the initially straight gut tube into the complex intestinal system of the adult chick. The focus of this study is on shape changes that occur between the fourth and fifth days of incubation when the straight gut tube is transformed into an s-shaped one (Fig. 1C). This occurs as the primitive gut tube undergoes rapid elongation, twisting, and rotation causing three distinct bends (the duodenal loop, umbilical loop, and the duodenal-jejunal flexure) to appear simultaneously by the end of the fifth day. Borrowing the term used to describe a similar process in heart development, this initial phase of gut looping is referred to as “s-looping of the gut” in this study.