We have recently reported development of a lumped-parameter model for several lymphangions in series [1]. The model provides for both active smooth muscle contraction (intrinsic pumping) and passive compression of the lymphatic by external tissues (extrinsic pumping). The valves which define the lymphangions vary their resistance sigmoidally, having a high (low) resistance for an adverse (favorable) pressure difference. With no refractory period between sinusoidal active tension episodes, maximum pumping efficiency was reached when each lymphangion contracted 135° after that immediately upstream; simultaneous contraction (corresponding to the situation of extrinsic pumping) was especially inefficient.
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