So...How should your large intestine work?

Before I started looking into my digestive system I assumed that the large intestine just continued to digest what had not been digested in the small intestine. How little did I know then!

For the majority of people, if they have problems with their digestive system, have problems with their large intestine or bowel! It has very specific jobs that it does, which are extemely important to your health. Once the digested material from the small intestine enters the colon, it takes around 16 hours for the remaining digestive process to occur but it can take a lot longer.

Structure of the large intestine

The large intestine is about 1.5m long. It differs from the small intestine in structure as it is wider and instead of having villi (finger like folds) it has invagininations (or intestinal glands). These glands contain cells that absorb water and goblet cells that secrete mucus into the large bowel. This mucus lubricates the walls of the large bowel and allows smooth movement of the contents through the colon.

Before the main part of the large bowel there is a pouch called the cecum which recieves the contents from the small intestine. The appendix is an attachment that has no real function but it can become infected. If this occurrs then it must be removed.

large intestine, colon

The rest of the colon is made up of 4 major parts:

  • The ascending colon
  • The transverse colon
  • The descending colon
  • The sigmoid colon

Then there is the Rectum and the Anal canal.
At regular intervals along all 4 parts of the colon there are pouches called haustra. The smooth muscle surrounding the colon (that is muscle that we have no control over) contracts in rhythm to produce haustral contractions. Through these contractions the contents of the colon are are mixed and forced from one pouch to the next.

So what are it's main functions?

The large bowel is mainly responsible for reclaiming or absorbing water, water balance, absorbing some vitamins, making some vitamins and breaking down undigested fibre from carbohydrates.

When the digested food (chyme) enters the colon, it is still a fluid. Although generally, about 90% of the water, and most of the nutrients that we can digest with the digestive enzymes we produce, have already been absorbed in the small intestine.

One of the main differences between the 2 intestines is that the large intestine hosts many kinds of beneficial bacteria (over 700 species). This is called symbiosis, where an organisism lives in or on another organisim in a mutually beneficial relationship. These bacteria are called probiotics or 'good bactiera'.

These probiotics have a vital role in the large intestine:

Firstly they breakdown undigested fibre (polysaccharides from carbohydrates). From this they produce important nutrients for their own survival and that are necassary for the health of the lining of the colon.

That is why, if our diet does not have enough fibre in it, these bacteria cannot survive to keep the colon lining healthy and functioning properly.

Secondly, they produce large amounts of vitamins including Vitamin K and many of the B Vitamins. In short these vitamins are vital for areas such as the nerves, red blood cells and healthy bones. Therefore, problems related to fatigue, dizziness, tiredness and lack of concentration could all be signs that your colon is not functioning properly due to problems with these bacteria.

When they not in the correct balance they can cause all sorts of issues. They have now been linked to colitis and ulcerative colitis and are very often the cause of irritable bowel syndrome.

I plan on doing another page as soon as possible in more detail about these probiotics. In the meantime please take a look at the candida page (which is a yeast infection in the colon caused by die off of these bactera) as I explain a litle more there.

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Go to What is candida albicans? page from The large instestine