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The small intestine is a long, highly convoluted tube in the digestive system that absorbs about 90% of the nutrients from the food we eat. It is given the name âsmall intestineâ because it is only 1 inch in diameter, making it less than half the diameter of the large intestine.
Absorption and egestion. These are the processes that happen in the digestive system: ingestion (eating) â digestion (breaking down) â absorption â egestion. We've already looked at how foods are broken down by enzymes in digestion. Now we will look at how the products of digestion are absorbed into the body. Absorption. Digested food molecules are absorbed in the small intestine. This means that they pass through the wall of the small intestine and into our bloodstream. Once in the bloodstream, the digested food molecules are carried around the body to where they are needed. Only small, soluble substances can pass across the wall of the small intestine. Large insoluble substances cannot pass through.