COLON, DRAWING. COLON, DRAWING The large bowel or colon is a 1.40 m long tube measuring about 6.5 cm in diameter. The colon begins in the lower right part of the abdomen at the end of the small bowel by a dead-end loop called the cecum to which is connected the appendix. The colon then ascends to the liver (ascending colon) the crosses the abdomen towards the spleen (transverse colon) before descending to the rectum (descending or sigmoid colon).