Intestine

The intestine (or bowel, or gut) is the segment of the alimentary canal extending from the pyloric sphincter of the stomach to the anus and consists of two segments, the small intestine and the large intestine. The small intestine is further subdivided into the duodenum, jejunum and ileum while the large intestine is subdivided into the cecum and colon.

In the intestine there are folds and twists which provide a huge surface area capable of absorbing all the nutrients.  There are finger like projections in the wall called villi adding to the surface area.  Each villus is supplied with a good blood supply and it is the blood that carries the extracted sugars, amino acids, minerals and other water soluble substances such as vitamins to the liver for further processing.  There are things called ‘lacteals’ which transport any fat soluble substances.  So it is here that differences between people can result – efficient intestine, inefficient intestine.

Once all the nutrients have been absorbed in the small intestine, the intestine contents, which are now in the form of faeces, pass slowly along the large intestine.  The main function of the large intestine is to reabsorb water into the blood stream, making the faeces less bulky.  This is a vital function, a lot of water enters the gut every day and if this were not reabsorbed we would become severely dehydrated.

So it is the duodenum that  is the site of intense chemical activity and the place where nutrients get extracted. 

Both the liver and pancreas supply chemicals that help in the absorption process, for example,  – lipase, bile salts and so on - all of which help to process the ingested substances, neutralising stomach acid, emulsifying fats, turning peptides into amino acids and so on.

The large intestine contains a number of different types of bacteria, for example Escherichia coli, that help in producing vitamins such as vitamin K and some B vitamins as well as folic acid, and biotin all of which are essential ‘fuel’ and building blocks for the body.  This area is not well understood and is under research, but it is clear that some of the bacteria offer a defensive role.  If compromised [for example using antibiotics] we can become ill.

“The human gastrointestinal lumen is inhabited by a wide variety of microbiota. Our understanding of the intestinal microbiota and its full consequences on gastrointestinal health is still evolving. However, it is well accepted that altered colonic flora drives the pathogenesis of many disorders and diseases as seen in antibiotic-associated diarrhea and Clostridium difficile infection. PMID:  23037903”

See also Boots Web MD for more images of the intestines.

Observations

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• Dismicrobism in inflammatory bowel disease and colorectal cancer: changes in response of colocytes.
• Gut microbiota: Description, role and pathophysiologic implications
• Immune protection of human milk
• The Roles of Inflammation, Nutrient Availability and the Commensal Microbiota in Enteric Pathogen Infection