The digestive process of a canine begins in the mouth, where the food is mechanically broken down into smaller pieces by the dogs teeth. The food is also chemically broken down in the mouth by the dogs saliva. The saliva is released into the mouth by the salivary glands. Saliva is ninety nine percent water and only one percent mucous. The saliva also aids in the swallowing of food down the esophagus and into the stomach.
Once the food reaches the stomach, the food is again chemically broken down by the stomach acid. There are specialized cells in the stomach that produce enzymes and hydrocodone acid. The food then proceeds into the small intestine through the pyloric sphincter, which is a valve in the stomach that closes right after the food passes through it to prevent it from going back into the stomach.
The small intestine is used to absorb the nutrients from the food that is eaten by the animal. The nutrients, such as water, carbs, proteins, vitamins, minerals and fats, are used by the animal for multiple things. Water is the most important nutrient for all living things, and can cause death the fastest if not provided. The amount of water that is needed is based on the activity, lactation, and the gestation of the animal.
After the food leaves the small intestine it them moves into the large intestine, which includes the cecum, the colon, and the rectum. The purpose of the large intestine is to absorb all of the water that the food, and the nutrients that are obtained are then moved into the liver.
The nutrients that a dog needs to survive are carbohydrates, which are made up of three different types, sugar, starch, and fiber. Although cats aren't suitable for high carbohydrate diets, carbs makes up at least 75% of an animal's diet. Lipids are also needed for a healthy diet, the fats supply the energy needed for a normal body maintenance, and contain the highest about of energy. Protein is a nutrient that is needed to grow new tissue and repair old tissue important for growth, weight gain, and gestation. Minerals are inorganic elements that are essential in a canines diet. Vitamins are organic elements that help the body turn food into energy and tissues, the vitamins needed are A, D, E, K, C, and B.