Multi-segment lymphatic vessel model based on lattice Boltzmann method

Abstract

The lymphatic system plays an important part in the body’s immunity and cell’s internal environment homeostasis. Like a blood circulatory system, the lymphatic system is a piping system throughout the body, which is composed mainly of lymphatic fluid and lymphatic vessels. The spontaneous contraction of the lymphatic vessels drives the flow of lymphatic fluid in the vessels. The spontaneous contraction-relaxation mechanism of lymphatic vessels is determined by the oscillating feedback of Ca<sup>2+</sup> concentration and NO concentration. The distribution of NO in the vessels plays an important role in the contraction cycle of lymphatic vessels. The shear force acting on the lymphatic valves due to the flow of fluid is the main source of NO. In a real system, the distribution of NO in a certain section of lymphatic vessel will be affected by other lymphanion connected to it, especially the upstream connecting fragments. Through the lattice Boltzmann method, a multi-segment lymphatic vessel model with valve structure is established, which reproduces the feedback mechanism of Ca<sup>2+</sup> and NO, valve change and fluid flow. There are three types of lymphatic vessels in the model, namely the initial lymphatic vessel, the collecting lymphatic vessel, and the outlet lymphatic vessel. The number of lymphatic vessels can be unlimited and inputted by the parameters. The number of lymphatic vessels is 3－5, and there are two pairs of valves in each lymphatic vessel. In this paper studied are the distribution of NO and pressure in multi-segment lymphatic vessel, and the change in the flow of each vessel in the three-segment vessel model over time.