|MadSci Network: Anatomy|
The human intestine is certainly a long structure. For example, the large intestine (comprising the caecum, colon and rectum) alone is over 1.5 metres in length (or 5 feet). The reason for this is probably because the intestines perform a variety of functions.
In the small intestine (comprising the duodenum, jejunum and the ileum, 3 metres in total), food coming from the stomach is continually mixed and stirred for further digestion. Absorbtion of nutrients, carbohydrates and fats then takes place all along the small intestines through finger-like structures called villi. The villi significantly increase the surface area of the intestines and therefore provide a large area for which all these "goodies" can then be absorbed. In addition to this, the small intestines may also perform other functions, for example, the ileum also has lymphoid tissue where white blood cells are available to destroy any harmful bacteria.
In the large intestines, water is reabsorbed and faeces are formed. Some cells in the colon also secrete mucus to lubricate the faeces and protect the intestinal lining.
If the intestines were short, it is unlikely that we'd be very efficient in absorbing all our nutrient and energy requirements from our food.
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