GASTROINTESTINAL
The human gastrointestinal tract refers to the stomach and intestine , [ 1 ] and sometimes to all the structures from the mouth to the anus . [ 2 ] (The "digestive system" is a broader term that includes other structures, including the accessory organs of digestion ). [ 3 ] In an adult male human, the gastrointestinal (GI) tract is 5 metres (20 ft) long in a live subject, or up to 9 metres (30 ft) without the effect of muscle tone , and consists of the upper and lower GI tracts. The tract may also be divided into foregut , midgut , and hindgut , reflecting the embryological origin of each segment of the tract. The GI tract releases hormones to help regulate the digestion process. These hormones include gastrin, secretin, cholecystokinin, and grehlin, are mediated through either intracrine or autocrine mechanisms, indicating that the cells releasing these hormones are cons...