sigmoid colon: the s-shaped curve between the descending colon and the rectum
colon: the part of the large intestine between the cecum and the rectum; it extracts moisture from food residues before they are excreted
corpuscular radiation: a stream of atomic or subatomic particles that may be charged positively (e.g. alpha particles) or negatively (e.g. beta particles) or not at all (e.g. neutrons)