The digestive system of dogs are quite different from a humans. Like a human the digestion process for dogs starts at the mouth, unlike humans dog mouths are designed to take in a large amount of food at one time instead of breaking it down first. After being swallowed the food goes down the esophagus which is the pathway that food travels through into the stomach. The stomach then breaks down the food using built in hydrochloric acid which breaks down anything that the dog eats, they also have a natural regurgitation instinct to spit out any food that has not been broken down properly.
After the stomach breaks down food into a liquid form the real digesting begins. The liquid broken down food is dropped into the small intestine where the nutrients of the food are assimilated into the dogs body. After this whatever is left is then sent to the large intestine which is the final stop before the waste product is sent to the rectum and ejected from the body. The dog has one of the shortest digestive cycles among mammals at around 8-9 hours which can vary for smaller and younger dogs.
Carbohydrates: The main energy source for the brain, without carbs the body would not function normally there are many sources for carbohydrates including: fruits, grains, starchy vegetables, and sugars.
Proteins: Proteins are the main structural material for cells and are used to grow and repair the body. Proteins are broken down into 20 types of amino acids 9 of which are considered essential. Meat, dairy, beans and eggs are all good sources of proteins.
Lipids: Fats store energy much better than any other nutrient, about 2.25 times more than carbohydrates. These are essential for dissolving fat soluble vitamins like A,D,E, and K.
Vitamins: These nutrients come in two different types, water soluble and fat soluble. Water soluble vitamins include: Vitamin C, B1, B2, B3, B6, and B12. The body needs a constant supply of water soluble vitamins in small doses to survive. Fat soluble vitamins include: Vitamins A, D, E, and K. Vitamin D is needed for the proper absorption of calcium, A is needed for proper eyesight and retinal repair, E is used to create antioxidants and to protect cell walls. Finally K is needed for blood clotting.
Minerals: Sodium helps maintain fluid volumes outside of cells and help cells function normally. Potassium maintains fluid volume inside and outside of cells and prevents the excess rise of blood pressure with increased sodium intake. Calcium helps to maintain and build strong bones and teeth. Water is by far the most important nutrient and is the one most needed to stay alive, Water helps to maintain homeostasis in the body and transports nutrients to cells. Water also assists in removing waste products from the body.