The gastrointestinal system has four main functions: ingestion, digestion, absorption, and metabolization The duodenum is the site for iron absorption and some vitamin B 9 (folate) absorption, but the major site for vitamin B 9 absorption is the jejunum

The large intestine has three main functions in digestion overall: absorption of the remaining water and electrolytes, absorption and production of vitamins, and formation and movement of feces to the rectum for… The small intestine handles 90% of nutrient and water absorption

duodenum — the site for iron absorption and some vitamin B 9 (folate) absorption, but the major site for vitamin B 9 absorption is the jejunum. digestion — the process by which the body breaks down what is ingested into absorbable substances. ingestion — the taking in of substances into the body through swallowing or transdermal absorption. absorption — the taking in of broken-down substances into the cells.