Henry Gray (18251861). Anatomy of the Human Body. 1918.
the Transversus abdominis, and the Quadratus lumborum (Fig. 1056). It is smaller in caliber and more deeply placed than the ascending colon, and is more frequently covered with peritoneum on its posterior surface than the ascending colon (Treves). In front of it are some coils of small intestine.
The Iliac Colon(Fig. 1076) is situated in the left iliac fossa, and is about 12 to 15 cm. long. It begins at the level of the iliac crest, where it is continuous with the descending colon, and ends in the sigmoid colon at the superior aperture of the lesser pelvis. It curves downward and medialward in front of the Iliacus and Psoas, and, as a rule, is covered by peritoneum on its sides and anterior surface only.
FIG. 1077 The posterior aspect of the rectum exposed by removing the lower part of the sacrum and the coccyx. (See enlarged image)
The Sigmoid Colon (colon sigmoideum; pelvic colon; sigmoid flexure) (Fig. 1076) forms a loop which averages about 40 cm. in length, and normally lies within the pelvis, but on account of its freedom of movement it is liable to be displaced into the abdominal cavity. It begins at the superior aperture of the lesser pelvis, where it is continuous with the iliac colon, and passes transversely across the front of the sacrum to the right side of the pelvis; it then curves on itself and turns toward the left to reach the middle line at the level of the third piece of the sacrum, where it bends downward and ends in the rectum. It is completely surrounded by peritoneum, which forms a mesentery (sigmoid mesocolon), which diminishes in