Figure 6

Results for a 10 minute recording of an in vitro rabbit distal colon. (a) a composite Diameter/Pressure Map (DPMap). In (b) each of the 12 possible mechanical states are mapped to different colors. The map portrays the periods of quiescence either when the gut remains passively dilated (light-green) or passively occluded (dark-green). Red, orange and yellow areas represent active contractions and mark the propagating area of contraction during neural peristalsis. Active relaxation (cyan and light-blue) precedes both in time and space the propagating contraction. In (c) we present a simplification of the full composite map of states by clustering all areas undergoing active contraction (red) and, active relaxation (blue). All other passive states are in white. (d)–(f) show an example of an instant (vertical line in (a)–(c); ∼ 3.5 minutes) where the liquid bolus between 190 mm and 230 mm is traveling down the length of the colon from left to right. The actual rabbit colon is shown in (d). In (e) the gut is color coded with the colors from the multiple mechanical states shown in (b). In (f) the simplified mechanical states from (c) are shown. The isotonic contraction at 190 mm (orange) and auxotonic contraction at 180 mm (yellow) push the bolus to the right, while the isometric contraction at 150–170 mm (red) ensures no back-flow. The isotonic relaxation at 210–240 mm (light-blue) help to expand the colon to accommodate the incoming bolus. The distended quiescence at 200 mm (light-green) depicts a momentary stillness where changes in diameter and pressure are trivial. The isometric relaxation between 80–140 mm (dark-blue) represents the recovery from earlier active contractions in that region that resulted in propelling the liquid bolus to the right.