Fig. 6. Simulated particle motions in the pharyngeal lumen. Simulated motions of three particles in the corpus and anterior isthmus. Anterior is to the left; the posterior end of each diagram (the pointed end) represents the middle of the isthmus. (The posterior half of the isthmus and the terminal bulb were not included in the simulation and are not pictured here.) The white region is the maximum possible opening of the lumen, and blue represents the opening at any particular point in time. Time in ms is given in the upper right corner of each panel. (A-D) Motions were simulated as shown in Fig. 5. (E-H) The isthmus was assumed to move in synchrony with the corpus, so that muscle motions are precisely reciprocal. (B,F) (83 ms) The beginning of anterior isthmus contraction, when the corpus is partly contracted; (C,G) (133 ms) maximum corpus contraction, and (D,H) the end of a full cycle. (Because the isthmus motions are not delayed in E-H, the cycle is only 150 ms long.) In A-D, each particle has a slightly more posterior position at the end of the cycle than at the beginning, i.e. there is net transport. In E-H, particles end up precisely where they began, showing that net transport requires the delayed isthmus motions shown in A-D.