We have mechanical digestion and we have chemical digestion and we'll see what the difference is between the two to in just a moment. Now our digestive system also plays a role in actually absorbing those broken down nutrients into our blood system and lift system and those nutrients eventually travel to the cells that require the nutrients to basically produce ATP molecules that are used as the energy molecules in our cells. So let's begin by discussing several important types of structures that exist within our digestive system. So let's follow the pathway of the food as we place it inside our mouth. Now the mouth portion is basically known as the oral cavity. This is where we place our food.