Small intestine
The length of the small intestine can vary greatly, from as short as to as long as , also depending on the measuring technique used. The typical length in a living person is 3m-5m. The length depends both on how tall the person is and how the length is measured. Taller people generally have a longer small intestine and measurements are generally longer after death and when the bowel is empty.
Retroperistalsis
In the small intestine, local stimulation of the intestinal smooth muscle by the presence of food particles causes contractions that tend to travel from the stimulated point in both directions. Under normal circumstances, the progress of the contractions in an oral direction is quickly inhibited, while the contractions travelling away from the mouth tend to persist. If the intestine is paralyzed by applying such drugs as nicotine or cocaine to the intestinal wall, the contractions initiated by local stimulations travel equally well in both directions. Ordinarily, peristaltic waves appear in the small intestine at irregular intervals and travel for varying distances; some travel only a few inches, others a few feet. They serve to expose food to the intestinal wall for absorption and to move it forward.