The digestive system extends from the oral cavity to the anus, paralleling the transit of the food bolus from ingestion to its conversion into feces, and therefore involves all the structures that participate in this process (mouth, pharynx, esophagus, stomach, liver, pancreas, small intestine, large intestine, rectum, and anus).

The importance of nutrition in animals lies in the fact that the digestive system forms one of their main protective barriers. In this way, it separates the external environment, the environment, and its internal environment, preparing food so that it can pass from the former to the latter without danger of intrusion by inappropriate substances, bacteria, or other harmful organisms, and preventing the loss of products from the internal environment to the outside.

Therefore, a first process takes place, digestion, consisting of breaking down the components of the diet into their simplest forms, so that they can be absorbed and used by the body.

The higher the biological value of the food, as well as the digestibility and nutritional value, the greater the absorption of nutrients.

The food is subjected to the action of various secretions produced by the body. These contain digestive enzymes that allow, favor, and accelerate the process of hydrolysis, in which water is responsible for breaking the bonds of food into its most essential components.

Among the main categories of nutrients, there are three whose digestion is especially necessary: carbohydrates, proteins, and lipids. There are also other nutrients such as water, minerals, or vitamins, which are absorbed in a similar way to how the food is found, so a digestion process as exhaustive as for the previous ones is not necessary, although it is necessary to separate them from these and be able to be correctly absorbed.

Even so, for digestion to take place optimally, it is necessary for some processes to be carried out jointly, which we will explain in more detail in another article.

As a curiosity, it should be noted that there are many differences between the digestive system of the dog and that of the human.

Among others.