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The ileum is a specific section of the digestive system, which is one part of the small intestine. Distal is an anatomical term describing the positioning of a body part relative to a central point. The distal ileum is actually the end portion of the small intestine, before it transitions into the large intestine. This particular area of the gastrointestinal tract absorbs nutrients and bile from the food breakdown process.
Each person's gastrointestinal system is separated into different segments, depending on their function. The small intestine, of which the distal ileum is part, follows after the stomach segment. In the stomach, food is mixed up with acid before it is moved into the first part of the small intestine. With three main parts to it, the small intestine consists of the duodenum, the jejunum and the ileum, in that order.
Bile and digestive enzymes are released from the liver, gallbladder and pancreas into the duodenum to further break down food. The enzymes cut up protein and carbohydrate substances, and the bile sticks to the fats so other specialized enzymes can break them down. After the duodenum, the food moves into the jejunum and then into the ileum. Most of the fat is absorbed before it gets to the ileum, but by the time the food gets to the distal ileum, most of the other nutrients are absorbed. In addition, the ileum collects the bile salts in the mixture and sends it back to their origin in the liver so the liver can use the material again.
As the end of the small intestine furthest away from the center of the body, the distal ileum portion turns into the start of the large intestine. By the time ingested food gets to this point, past the distal ileum, all that is left is the fibrous component of the food and liquid. The large intestine then absorbs excess water and salts from this substance and turns the remainder into waste.
Individual portions of the digestive system perform different jobs and therefore have specifically evolved cell linings. The ileum is lined with cells that form many little folds on the inside of the digestive tract. Each of these little folds contains a network of tiny blood vessels close to the surface. When nutrients or bile salts come into contact with the folds, they move through the cells and into the blood vessels, which carry them away to other parts of the body.