|MadSci Network: General Biology|
I have been able to find no evidence that gravity aids digestion. It certainly can't hurt; after all, we evolved in an environment with gravity. It seems natural that gravity would help pull the food down the esophagus, hold it down in the stomach, and help it move into the intestines. Gravity would also seem to help in the process of eliminating the final outcome of digestion. But I can think of no place where food merely falls, or is allowed to rest. All of these processes occur because of the movements of the various muscle groups associated with the digestive system. Muscles in the esophagus push food down (patients with paralysis of the esophagus are unable to swallow.) Food doesn't rest calmly in the stomach; instead it is squeezed and mixed with various juices and enzymes. The squeezing process also moves food out of the stomach into the small intestines, where muscles continue to move the food along the loops and twists and turns. Finally, both defecation and urination can happen without the assistance of gravity, as anyone who has had to change the diaper of a baby lying on its side can tell you. NASA's website, www.nasa.gov, has little information on this subject. The best I could find was a question from an Australian schoolkid to Andrew Thomas, an American astronaut that spent some time on Mir. He reported no effects to his digestion. http://spaceflight.nasa.gov/history/shuttle- mir/mir25/status/week12/thomas.html This was a great question that provoked some interesting thoughts! I hope the debate continues in a friendly manner. Thanks for using MadSci! Regards, S. Kohler, your Mad Scientist du jour
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