Abstract
The lymphatic system is an extensive vessel network featuring one-way valves and contractile walls that pump interstitial fluid, proteins, and immune cells through lymph nodes and then back to the blood circulation. This system is crucial in immune response, as well as being the pathway of distribution for metastatic tumor cells. Failure to drain and pump results in oedema, or fluid retention and swelling.
We are developing multi-scale computational models of lymphatic function from the sub-cellular to the whole organ level in conjunction with a series of experiments. Models of vessel segments in series have been characterized through pump curves of steady pressure difference versus flow rate. These curves exhibit non-linear behaviors typical of mixed source pumps. These models also provide the opportunity to quantify the importance of various modeling parameters through sensitivity analysis. For example, the phase angle between successive lymphangion contractions is an important determinant of pumping efficiency, with out-of-phase behavior being the most efficient.
Experiments with rat mesentery lymphatics revealed that these vessels quickly adapted to increased volume loads by increasing lymph flow rate and contraction frequencies. Valves are biased toward the open position, with that bias increasing with transmural pressure.
Unlike arterial and venous vessels, the lymphatic system has not been the subject of extensive modelling efforts. Our work is aimed at constructing models that strike a delicate balance between the need to represent complex physiological phenomena and the desire to keep the modelling feasible computationally.