This chapter describes the development of the gastrointestinal tract and illustrates the important topographic anatomy with a focus on mesenteries. During the early weeks of the embryo, the primitive gut tube is suspended from the body wall by mesenteries that enclose the organ and connect it to the body wall, providing pathways for vessels and lymphatics to and from the abdominal viscera. With rotations of the stomach and the midgut loop, the mesenteries undergo complex deformations, positional changes, and fusions to adjacent organs. Understanding these embryological processes will be helpful in recognition of anatomical pitfalls, and the application of such knowledge is advantageous in laparoscopic colorectal surgery.