Small intestine
The length of the small intestine can vary greatly, from as short as to as long as , also depending on the measuring technique used. The typical length in a living person is 3m-5m. The length depends both on how tall the person is and how the length is measured. Taller people generally have a longer small intestine and measurements are generally longer after death and when the bowel is empty.
Gastrointestinal tract
The gastrointestinal tract forms an important part of the immune system. The surface area of the digestive tract is estimated to be about 32 square meters, or about half a badminton court. With such a large exposure (more than three times larger than the exposed surface of the skin), these immune components function to prevent pathogens from entering the blood and lymph circulatory systems. Fundamental components of this protection are provided by the intestinal mucosal barrier which is composed of physical, biochemical, and immune elements elaborated by the intestinal mucosa. Microorganisms also are kept at bay by an extensive immune system comprising the gut-associated lymphoid tissue (GALT)