You can't ignore the importance of a good digestion. The joy of life depends on a sound stomach, whereas a bad digestion inclines one to skepticism, incredulity, breeds black fancies, and thoughts of death. The intestines are the parts of the digestive system responsible for the absorption of nutrients, but they could not function properly without the pancreas , which produces the digestive enzymes used for the process.
Many people have the erroneous idea that the intestines actually secrete digestive enzymes.
The intestines represent a nice application of a general rule in anatomy. If you want to improve the efficiency of a process which is associated with or limited by a transmembrane phenomenon, the way to do it is increase the surface area . Most of the general structure of the intestine is similar throughout, and the overall description given here for duodenum is appropriate for the jejunum and the ileum as well. Where specific regional variations are present they will be described. The lumen is lined with short, uniformly sized villi, all quite regular in size and shape.