1. In our mouth, the chewing action of our teeth, also known as mastication, a mechanical digestion, breaks down food into smaller pieces. Combined with our saliva that chemically digests the food, it becomes an easy to swallow food ball called bolus. As the bolus reaches the stomach, it is mixed with stomach acids for further digestion, thus turning it into a soupy mixture called chyme. Lasly, in the large intestine, undigested materials and most water is removed, thus changing chyme into a solid form, which is called feces, for excretion.
2. Most of the absorption of nutrients happens in the small intestine. The small intestines contain villi, which are tiny fingerlike projections that increase the surface area for absorption. These villi have very rich blood supply, thus when food passes through them, nutrients are easily absorbed into the bloodstream, then delivered throughout our body.