Relationship Between Intestinal Blood Flow and Motility

namely by evoking a metabolic hyperemia and by causing an extravascular com­ pression. These produce opposite effects on local blood flow, and their interplay in the regulation of blood flow in the heart and skeletal muscle has been well demonstrated. The effects of muscle contractions on blood flow in the gut, however, are different from effects in the heart and skeletal muscle, since intestinal contractions are random in time and space, and vary in rhythm, strength, and duration. Segmenfal contractions, the most com­ mon type, involve only 1-2 cm of intestine and last 3-8 seconds. Therefore, unless blood flow is measured at the site of contraction, the compressive effect of the contraction may be offset by relaxation of adjacent areas. Since the blood vessels of relaxed regions freely communicate with those at an adjacent site of contraction, the overall effect is no net change in blood flow measured in a sizable intestinal artery . Even when the entire gut segment