Re: What if we had no intestine? Could one organ do it?

An interesting question - "what if we had no intestine". Well, a very straight answer would be that even if we had no intestine, we would be able to go to the bathroom, but the food we take would not be digested and absorbed well to keep us healthy.

Let's see this a bit more further.
The digestive system in us humans (and in most other animals) starts from the mouth (where food is taken in) and ends in the anus (where all the waste is passed out). And the basic functions of the system include ingestion (taking food), digestion, assimilation (collection and absorption of nutrients from food) and excretion (throwing out the waste).

When we take in food, most of it is digested in the stomach and duodenum. The basic function of the intestines comes in assimilation and absorption of nutrients from the digested food, and these nutrients provide the body with the energy to function. The nutrients can be carbohydrates, proteins, fats, various minerals, etc.

So, basically, it comes down to the point that, if we had no intestine, we would not be able to get the best out of what we eat. We would get no nutrition, no energy for the body to function.

Yes, I forgot to mention that the intestines are in two forms - the small intestine (where assimilation occurs) and the large intestine (where excretion occurs). So loss of small intestine causes problems in absorption of nutrients.

The large intestines work for excretion. After absorption, whatever is lef behind, is passed on to the large intestine, to excrete out. Here, extra water is absorbed, and that is what gives our stools their solid/semisolid consistency. So, it would seem that loss of the large intestine would have us not going to the bathroom.

But, in clinical practice, we often come across cases where either the large or the small intestines have to be removed, or due to some disease, the intestines dont work properly. Let's take the small intestine first.

To just quote an example, there is a set of disorders called "Malabsorption syndromes" wherein, the small intestines are not able to absorb certain nutrients, and causes problems. So what is done is that such people are advised to cut down on foods which cause them problems. On the other hand, if surgery is to be done, then we try our best to preserve as much of the small intestine as possible, so that at least some amount of absorption occurs.

For the large intestine, remember the time when you had loose motions?? Well, that is how they malfunction. As I said above, large intestines absorb water. If for some reason they dont do so (as in food poisoning or cholera), then what you have is diarrhoea. Also, again, if surgery has to be done on the large intestines, where a portion of it has to be removed, then, we provide an alternative route for excretion - what is known as a "colostomy". Here, after the diseased portion is removed, a small part of the large intestine is brought out on the surface through a small hole. This is then covered with a bag (colostomy bag) which is disposable, and collects all the excreted matter.

Hope this answers your query...
By the way, let me also tell you that the digestive system has evolved over ages to suit each and every species on the planet. There are species, which have just a single tube from the mouth to the anus, which acts as one organ for digestion, assimilation, and excretion, like worms for example. A zoologist might be able to explain that to you better than me!!