The Lymphatic System
This is a vital function . The body would expire within a day without this process. To the degree that this system doesn't perform properly the body health is effected.
The proper condition of the cell membranes is to have all the fluid inside and very little excess fluid in-between the cells. If there is excess fluid in the membranes then the flow from the blood system is reduced as it has to overcome the pressure of the fluid between the cells. If the lymphatic system is performing properly , producing a low pressure state in the membranes then the blood circulatory system functions much better.
The lymphatic system has one way valves all along the lymph vessels. These one way valves produce flow when the body moves. Both the squeezing muscular motion and the up and down action of activity pump the fluids.
You do not have to perform vigorously to get great benefit. Walking or soft bouncing on a mini tramp is an excellent way to pump the system. You must have body activity for the system to perform. If your body becomes inactive the system will not work and the body will slowly expire from this lack of use.