Answer:
The topic of nutrition, and especially of all the process of digestion, absorption and use of the nutrients afforded to humans through food ingestion, thanks to the G.I tract. Without our gastrointestinal system, we would simply be incapable of living. Among the many organs that make part of this system, and one of the most important, is the small intestine, a long tube of several feet of length whose tissue, and structure, ensure that the food that has been turned into chyme, is mixed with the chemical enzymes that will give our bodies access to the nutrients in the food, and these can be used by the body.
1. The small intestine is divided into three different regions: the duodenum, where most of the mixing of the chyme with enzymes takes place, the jejunum, where most of the absorption of nutrients happens, and the ileum, where absorption also takes place.
2. The segment where most of the absorption takes place is the jejunum, where, with the exception of iron, vitamin B12, vitamin B9 (this one is also absorbed in the duodenum), and others.
3. The nutrients that are absorbed by blood capilaries, and do not need any mediation to enter the bloodstream, as they enter in their most basic forms, are proteins (aminoacids and carbs).
4. The nutrients that are absorbed by the lymphatic vessels, known as lacteals, are the lipids, as they still have some more breaking-up to do, in order to pass, in their most basic forms, to the blood.
