Some stuff rattling around in my head:
Chinese medicine groups the body's various parts differently than does Western medicine. We group according to type of tissue – bone, nerve, muscle, etc. – whereas the Chinese group according to function. In their system, the gut, lungs and brain are all grouped together because they all are similar in function (i.e. nutrition in – waste out in the same movement).
In Western astrology, Mercury, the planet that rules intellect, also rules lungs and intestines.
I have also always trusted my gut instincts. They rarely steer me wrong.
These rattlings come together in this article about the body's second brain: The gut.