The human digestive system plays two important roles. It digests our food and also absorbs our food. Now digestion refers to the process by which we actually break down our macromolecules into their constituents and we have two types of digestion. 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.