Answer:
The answer to these multiple questions is pretty broad and long because the GI tract is probably one of the most diverse, complex, and function-filled systems of the human body.
1. To begin with, the GI tract has a main purpose, which is to ingest, digest, process, absorb and excrete the unnecessary waste that comes from the processes mentioned before. All of these have to do with fulfilling the main function of the GI tract, which is, to provide nutrients to the body through food and fluid intake. In order to fulfill this purpose, the tract is packed with muscles, accessory organs, blood vessels, nerve terminals and innervation and lymphatic vessels that willl aid in this process.
2. During the passage of food through the system there are a series of chemical steps that need to be taken, in order to be able to substract the necessary nutrients from food. In order to do this, the body counts with enzymes, chemical proteinic substances produced by different GI organs to ensure proper digestion and absorption of nutrients. Among the ones that we have are: amylase, pepsin, tripsin, pancreatic lipase, deoxyribonuclease and ribonuclease. All of these work on different molecules in food, like fats and carbs, and will allow the body to use them.
3. The GI tract also has hormonal activities, mostly related with the correct functioning of the entire system when food is present and nutrition is a must. Some of the enteroendocrine hormones are: gastrin, cholesystokinin and secretin, only to mention some.
4. The bacteria that populates our GI tracts are known as enterobacteria, they are mostly gram negative bacteria, like E. Coli, whose function is to further aid in the extraction and digestion of nutrients in food, once the chyme reaches the large intestine. These bacteria are from the enterobacteriaceae family and comprise more than 200 species.
