The valve system (explained in detail on the valve system explanation page) is responsible not only for circulating body fluids and blood, but also for creating internal pressure as a result of the valves (or diaphragms) pumping. Internal pressure does useful things like helping our body hold its shape and responding to external pressures pushing in on us. Another crucial function is the stimulation of smooth muscle for motility and function. The smooth muscles that our organs are made of move only in response to pressure. The digestive system can only move and digest food when the valves are pumping and creating internal pressure. When this doesn’t happen, food may move through the digestive track very slowly, or our digestive system might have trouble breaking down more complex foods like gluten. The variety of symptoms that come from a poorly functioning valve system might lead to diagnoses such as irritable bowel syndrome, food allergies, or other digestive disorders or stomach problems. Again, when the body is in the parasympathetic nervous system state, the valves can pump, internal pressure can increase, and digestion will improve.
See the video resources page for a short animation on how digestion is controlled by the wave-like contractions of the smooth muscle called peristalsis that result from healthy valve system function.