Functional Relationship Between the Gut and Other Tissues/Organs of the Body

Abstract

The enteral system provides a pivotal functional connectivity with other organs and tissues of the body, referred to as gut-extraenteric tissue axis. This functional relationship regulates several functions of the body including higher mental (memory, cognition), cardiac, renal, pulmonary, hepatic, pancreatic functions. Examples of such relationship include gut-brain (enterocerebral) axis, gut-liver (enterohepatic) axis, gut-pancreas (enteropancreatic) axis, gut-liver-pancreas (enterohepatopancreatic/enteropancreatohepatic) axis or triangle, gut-heart (ente-rocardiac) axis, gut-kidney (enterorenal, enteronephric) axis, gut-lung (enteropul-monary) axis, gut-bone (entero-osseous) axis, gut-skin (enterocutaneous) axis, and gut-brain-skin (enterocerebrocutaneous) triangle. Other axes (usually referred to as systems) include hepatobiliary, pancreatobiliary, and pancreatohepatobiliary systems. These axes, triangles, and systems play a crucial role in the maintenance of homeostasis not only in the GI tract, but also in extraenteric tissues/organs. It is important to note that apart from the functional relationship, some of these axes, triangles, and systems are structurally connected to the gut. This chapter is concerned with this functional and structural connectivity. Keywords Gut-liver (enterohepatic) axis Á Gut-brain (enterocerebral) axis Gut-pancreas (enteropancreatic) axis Á Gut-liver-pancreas (enterohepatopancreatic/ enteropancreatohepatic) axis or triangle Á Gut-heart (enterocardiac) axis Gut-bone (entero-osseous) axis Á Gut-kidney (enterorenal, enteronephric) axis Gut-lung (enteropulmonary) axis Á Gut-skin (enterocutaneous) axis Gut-brain-skin (enterocerebrocutaneous) triangle Á Hepatobiliary Pancreatobiliary Á Pancreatohepatobiliary system Á Small intestinal bacterial overgrowth Abbreviations cAMP Cyclic adenosine monophosphate CCK Cholecystokinin cGMP Cyclic guanosine monophosphate GDP Guanosine diphosphate GI Gastrointestinal