A dogs mouth is made to get the food down; their bottom jaw is formed making it impossible to grind back and forth like a cow. So when our dogs seem like pigs and swallow things down whole, this is because it is how they work. Typically a dog will crunch their food into bite sized pieces that they can swallow down. Other times when they are far too exhuberant they may attempt to swallow down a piece of food that is much too big. This is common practice with my Jack Russell. Dogs may choke for a bit until it goes down or throw it up and give it another go.
Once the food goes into their stomach there is a recognition of food to be digested and a dogs pH level drops down to as low as 1 becoming highly acidic; so acidic in fact that it would literally burn a whole in our skin if we were to touch it. There the digestive enzymes get to work breaking down the food into molecules that the body can use. Once the stomach has digested most of the bulk food it is passed down to the small intestine where the liver and pancreas produce more enzymes for further digestion. From there it enters the large intestine and you know where it goes from there.
Dogs are not meant to eat the way we eat; they have entirely different food requirements and luckily there are a few good dog food companies out there that are heading towards that goal. But as with anything else in our consumer driven world there are far too many just trying to make a buck and are not concerned with our dogs at all. Do your research before you grab a bag of dogfood and if you can buy it at the big box store or the grocery store, you probably shouldn't be buying it.
Check out your local private pet store (of course the ones that do not sell puppies or kittens) to see what they carry. Many of the small family owned stores carry the good stuff. And if they are really good they will have several freezers filled with frozen raw, bones and prepared cooked food available for purchase. You can feed your dog complete balanced diets of raw food that has been frozen, simply thaw and feed. It is a great alternative to bagged dry or canned.
Variety is the best way to ensure balanced nutrition.