Your large intestine, or colon, is the final stop in your digestive system for your food. It is a wider tube than the small intestine totalling about 1.5 metres in length. It has smooth muscle surrounding it to help propel the waste through the tube. Your large intestine is broken down into 5 main sections: ascending, transverse, descending, sigmoidal and rectum.
After most of the digestion and absorption has occurred in the small intestine, the food passes into the large intestine where it functions to absorb as much of the remaining nutrients as possible. The food enters the large intestine as a liquid and will eventually leave solid. At the end of the food journey, over 90% of the nutrients and water have been absorbed.
The large intestine has a number of specific jobs:
- Absorption of water to keep your body hydrated.
- Absorption of remaining nutrients that got past the small intestine. This can include vitamins made by resident bacteria.
- Compaction of the indigestible waste into feces.
- Housing for your bodies gut flora (bacterial community or microbiome).
The most rapidly evolving field of research is into the role of this microbiome on your health. Your large intestine houses over 700 different species of bacteria, fungi, and protozoa that total around 100 trillion in number. These bacteria are important in producing many vitamins your body cannot make on its own and digesting some of the fibre in your diet. They are also important in educating your immune system against invading pathogens. The species in your large intestine can vary depending on where you live and the composition of your diet. There is mounting evidence that alterations in the composition of this bacterial community may play a role in diseases like cancer, obesity, and irritable bowel disorders.