SMALL INTESTINE

=Small Intestine= [image:http://i.imgur.com/Kcsaw8w.png?1] Following partial digestion in the stomach, food enters the small intestine. The small intestine is responsible for much digestion and the absorption of food. The small intestine consists of three parts: ''duodenum'' ''jejunum'' ''ileum'' ==The Duodenum== The duodenum is the first part of the small intestine and plays a major role in the ''digestion'' of food. [image:http://i.imgur.com/HbhFQLA.png?2] '''The Pancreas''' - secretes ''pancreatic juice'' into the duodenum. Pancreatic juice contains: • ''Digestive enzymes (Protease, Lipase, Amylase)'' • ''Bicarbonate ions'' that neutralise hydrochloric acid '''The Liver''' - produces ''bile'' that is the collected in the ''gall bladder'' and then released into the duodenum. Bile is.. • ''An Emulsifier'' that helps disperse lipids, increasing the surface area available for chemical digestion by lipase. • ''Alkaline'' and helps neutralise hydrochloric acid ==The Jejunum & Ileum== The jejunum (also called the mid gut) and ileum play a major role in the ''absorption'' of food. Food must first be digested in order to produce nutrient molecules that are ''soluble'' and ''small'' enough to diffuse across the intestine surface and into the blood stream. [image:http://i.imgur.com/9MwwXYc.png?1] '''Villi''' The small intestine is lined by millions of tiny 'finger-like' projections or folds called ''villi'' (singular villus). These increase the ''surface area'' of the small intestine without significantly increasing its size (volume). Each of the cells lining the villi have many tiny folds themselves that further increase the surface area, called ''micro-villi''. If the small intestine surface could be flattened out, it would cover a tennis court. The large surface area of the small intestine increases the the rate at which nutrients can diffuse into the bloodstream and ensures that sufficient nutrients are absorbed. ===Capillaries=== Most of the soluble nutrients including amino acids, vitamins and minerals diffuse into tiny blood vessels called ''capillaries'' and are transported though the body by the bloodstream. ===Lacteal=== Each villus also contains a tiny lymph vessel called a ''lacteal''. Fatty acids and glycerol molecules diffuse into the lacteal and are transported through lymph vessels (a network of tubes that are similar to blood vessels).