English: The image differs from from the original in that it sections the small intestine into duodenum, jejunum and ileum and a closed epiglottis has been added. Like no other illustration I know of, it offers the view that the duodenum and jejunum are short small bowel sections with the ileum overwhelmingly the greatest length section of the small bowel. It might interest you that digestion of food, here meaning protein, carbohydrate and fat, is complete before the leading edge of the food ever reaches the ileum. In the instances of proteins and carbohydrates, this is because the duodenum and jejunum are 'loaded' with membrane bound enzymes and additionally the active transporters needed for the efficient absorption of amino acids and monosaccharides that are enzymatically produced. It is also because the pancreas 'dumps' a rich supply of soluble enzymes into the duodenum as food enters the duodenum. It's also because the physical chemistry of the medium within the small bowel is managed so that the enzymes can be most active. The digestion of fat is different, but fat (triglyceride and phospholipid) is also scrubbed free from the small intestines before any reaches the ileum. The ileum functions to absorb nutrients that aren't actively transported into the body. Most drugs rely on the ilium for their absorption. In many instances absorption is also continued after passage of substance into the large intestine.