Digestion - How the Small Intestine Digests Food

If you open your hand and place it flat against your belly button, your hand is now covering most of the relatively small space that the small intestine is neatly coiled. The small intestine is roughly 20 feet long. When the soupy, partly digested food (chyme) spills from the stomach into the small intestine, this starts a new digestive process.

The small intestine is responsible for releasing gastric juices such as pancreatic and intestinal enzymes which finish the digestion of proteins and amino acids. Bile, which is a greenish liquid, allows fats to mix with water. Alkaline pancreatic juices make the stomach chyme less acidic so that complex carbohydrates can be broken down into simple sugars. And finally there is intestinal alcohol dehydrogenase, which digests alcohol that has not already been absorbed into the bloodstream.

When all of the above chemicals are working, the small intestine contracts and continues to move food down though the tubes in order for your body to absorb amino acids, sugars, fatty acids, vitamins and minerals.

The lining of the intestine is made up of a series of folds which are covered with projections that have been called "small fingers". The technical term for this is called villi. Each villus is covered by even smaller projections called microvilli. Every single villi and microvilli is programmed to accept a specific nutrient and no others.

Nutrients are not absorbed in the body by the order of their arrival. But by how fast they are broken down into their basic parts. Carbohydrates are quickly separated into simple sugars and as a result are absorbed first. Proteins as amino acids are absorbed next. Fats which take the longest to break apart are last.

This is why a high fat meal keeps you feeling fuller as it takes longer to digest than a vegetable salad.

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