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Published byBelinda Owen Modified over 9 years ago
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The first part of the small intestine is called the duodenum. The duodenum is only 25 cm long, but most of the digestion takes place in this region.
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Small amounts of chyme are ejected approximately every 20 seconds from the stomach into the duodenum.
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Also opening into the duodenum are ducts from the pancreas and the gall bladder. These allow enzyme-rich pancreatic juice and bile to be released and mixed with the chyme.
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Chemical breakdown of carbohydrate, protein and fats into smaller absorbable molecules takes place.
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Peristaltic waves of muscular contraction mix and move the chyme down the duodenum and into the jejunum, measuring about 2.5 m long.
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Peristaltic waves of muscular contraction move the chyme through the jejunum until it reaches the ileum.
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The jejunum has a huge surface area created by finger-like structures called villi. These assist with the absorption of nutrients into the bloodstream.
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Villi play an important role in absorbing the breakdown products of digestion. The increase in surface area, allows for ready absorption of these products of digestion.
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With villi Flat surface Nutrients to bloodstream
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Each villus has a rich blood supply, allowing nutrients to be readily absorbed and transported to the liver. A lacteal is also present; absorbing fat nutrients and carrying them to the circulatory system.
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