THE COMPONENTS OF A DOG'S DIGESTIVE SYSTEM:
The visible components are the organs and the physical remedies the dog has available to digest food. There are some significant and very obvious differences to what you have in your body. These are fairly easy to understand, because the differences can be observed,even by a layperson. The teeth are the most profound example.
But there are also some huge differences in chemistry. Chemistry is, unfortunately, not very many people's favorite discipline. It can be very complex and difficult to comprehend,but it is paramount for your ability to make sound decisions based on a good understanding
of your dog's needs that you do understand some of the basic chemistry.
It is not my purpose to make you fully educated in neither physiology nor chemistry - but I
hope I can give you enough understanding of those topics for you to at least feel the "aha effect" when you see the perspective of why things are as they are.
The dog’s digestive system (= gastrointestinal system – or GI system for short) is
o The mouth, with teeth, jaws, and saliva
o The esophagus
o The stomach, with connections to the pancreas and the liver
o The intestine
o The colon with its bacterial flora
o The rectum with anus.
Although there are many fundamental similarities between the human system and the dog’s
system, there are also many very significant differences.
The mouth, including teeth, jaws, and saliva
When you look at a dog's mouth, you will easily see how different its teeth are from yours.
The fang teeth are there to grab and hold and tear. The front teeth are there to scrape meat off bones. The incisors (small "saw teeth") are there to grab and hold. The big incisors are there to cut - acting as a pair of scissors. And the molars in-behind are there to
The jaws are fairly long, compared to the face (except for breeds that have been deliberately manipulated by human breeding to provide a shorter, more human-like face),
enabling the fang to grab quite large objects. The muscles that control the jaws are some of the most powerful muscles in the dog's entire body.
One more important thing, which you might not have noticed yet, the dog cannot move its jaws sideward! You can move your lower jaw from side to side, enabling a grinding process when you chew your food. Your dog cannot do that. The fang teeth make it impossible,and the jaw joint is a stiff hinge joint, like your knee joint - it does not allow any flexible movements other than up and down. If your dog trusts you well, it might allow you to test this by trying to gently move its lower jaw from side to side - but if you ever get your hands on a skull of a dog, you can very quickly verify this.
Already from this, we can make some important conclusions:
Humans who lack all their teeth get sick or malnourished because they do not digest their food properly. Chewing is important to us. Our stomach does not handle big chunks of food very well. And it also does not deal well with food that has not been properly mixed with saliva.
We know that our saliva contains some important chemicals that assist in the chemical processes of breaking down the food into smaller molecules our body can absorb and use.
These chemicals are called enzymes, and enzymes are characterized by stimulating chemical reactions in other molecules they come in contact with, without them being
destroyed in the process, as normally would be the case in a more "traditional" chemical reaction. They act as catalysts.
These enzymes are absent in dog saliva! Dogs have no need for chewing their food. They can't. Their stomach takes care of all the digestion, without any support from the saliva. The dog's saliva serves the purpose of being a lubricant for swallowing so the food easily
gets through the esophagus, and that's about it!
The canine stomach - and how it digests food
The dog's stomach is like an accordion that folds to almost a thin intestine-like organ when it is empty, and when filled, it expands to full size, unfolding all the wrinkles. In fact, when it is empty, it looks almost like a human brain – that’s how much it folds. (In comparison, a
human stomach is simply a bag – it does not fold at all.) The stomach has some very strong muscle in its lining, and it will constantly massage the food, thus making sure the
digestive juices get into close contact with the food.
The dog's stomach will take up some 70-75% of the total volume of the entire gastrointestinal system. It is huge. The human stomach will be only a small fraction of the
system, taking up only about 20% of its total volume.
The stomach will continue the digestion process till more or less all digestible pieces of food have been dissolved. When finished with the digestion process, the strong muscles will squeeze the now liquid mass into the intestine for the final finish of the process and for the absorption of the nutrients.
In general, all this is geared towards the stomach handling big portions of food at a time -and being given the opportunity to finish a meal before being filled again. It is like a washing machine running through its program and then waiting for the next load.
I hope you understand the huge difference compared to the human system that is much more like a septic tank where the food seeps through all the time. Our stomach does not
handle big meals very well. We do much better on a meal plan that gives us many small meals during the day, if not a constant flow of small snacks. Our stomach is way too small to do any serious digestion of large batches - it merely provides a brief pre-digestion by preparing the food for a more thorough digestion in the intestine.
The dog's stomach is a depot organ - the human stomach is merely a transit station.
Another important aspect that is often ignored is that a dog’s stomach is not supposed to be working constantly. It is meant to do a lot of hard work for some time – and then rest for a long period of time. It makes sense that it needs rest, considering how much harder it has to work, compared to a human stomach. Yet, a human stomach generally gets some serious rest every night. Our meals typically take no more than about 3-4 hours for the stomach to finish and hand over to the intestine, so even if we get a “good night snack” just before bed time, there will still be 4-6 hours rest available for the stomach before breakfast.
For the dog, digestion of a full meal can easily take more than 24 hours….
Another important aspect of the stomach’s function is the connection between the stomach resting and the liver functioning in a different mode! The essence of this very complicated process is that, as long as the stomach is active and digests food, the digested nutrients will
enter into the blood stream, typically through the intestine. Those will include many smaller molecules, also small carbohydrates that can be used by the body immediately as fuel.
Basically, while this happens, the liver is running mainly a “garbage clean-up” production;it does not do much to contribute to the production of simple carbohydrates. But, when the
The intestines and finishing the digestion process:
The intestine handles the food on a continuous basis, like the workers along a conveyor belt in an assembly plant. The food comes in at one end and then gets pushed through the
intestine until it comes out of the other end. The food travels along the intestines as time passes on. The specific position of it along the length of the intestine is determined by the time it has spent in the intestine. Food that is close to the stomach has not been in the
intestine for very long, whereas food that is close to the colon has been traveling through almost the entire intestine.
The relative length of the intestine tells us a lot about the role of the stomach. For the dog,the short intestine reveals that the stomach is where the main digestion takes place. For a human, the long intestine indicates that the stomach's role in the digestion process is nothing more than a preparation for the "real digestion" that takes place in the intestine.
The colon and its bacterial flora:
Finally, when the small intestine has done its job, the remains of the liquid food mass is passed to the colon. The colon's main function is really to absorb the water from what now is going to become the stool. Water is important as transport medium for the enzymes, and when their job is done, the dog might as well make good use of all the water in the mix. This is the same as for a human.
As the colon dries the food mass, these bacteria have a chance to thrive on the remains of the food, and, in the process of them eating some of it, they also generate some additional nutrients which the colon will absorb too. Sometimes, however, these bacteria will generate
some gasses also, through some fermenting-like processes. Dependent on the food sources and also on the specific bacteria in the colon, these gasses can be more or less offensive to a human nose…
Diarrhea and runny stools:
This means that the speed the colon uses to do its job is linked to the speed the intestine sets. If the intestine speeds up, the colon has to do the same thing - it cannot
accumulate any partially digested food.
This becomes important because a fast processing from the colon's side means a lowefficiency for the water absorption - which, in turn, means "loose stool", if not diarrhea….
Humans often get diarrhea because of bacterial infections in the stomach. It is, for us, a symptom of us being sick.
For the dog, this is not necessarily the case. The strong acid in its stomach will kill practically all of those bacteria that would normally harm a human. But that would not make the intestine speed up the absorption process…
Although the unpleasant gases are discharged through the anus, they are normally generated in the colon. The reason is almost always that there are imbalances among the
bacteria that live in the colon. Some bacteria ferment parts of the food – and generate those gases in the process.
The problem is not simple to deal with. To solve it, you need to get the bacterial flora in the colon back to its natural balance. To do this without a clue as to what exactly it is that is out of balance is quite challenging, to put it mildly.
Sometimes, a change of the food can work, avoiding specific foods that nourish the “wrong”
bacteria. Certain foods will typically make the situation worse than others. You can then
simply try to avoid the “trouble-makers”. Carbohydrates are very often major culprits for
this, but excessive vegetables of many kinds can easily nourish such fermentation
Sometimes adding certain supplements can do it. There are many herbal remedies that will have those kinds of effects of the bacterial flora in the colon; many bacteria do not like certain herbs – so if you can find the right combination of herbs that will work on the exact
problem you are dealing with, you can solve the problem.
The following articles are all available at K9joy’s web site at http://k9joy.com/dogarticles.
Reference: Mogens Eliasen