- Food enters our mouth (oral cavity), where chewing (physical breakdown of food) and hydrolysis (enzyme-assisted breakdown if food) takes place. As the food continues to break down in the oral cavity, the aim is to make a bolus, a sphere of digestive food. The food then goes into the esophagus, where food is propelled. Next, to the stomach. Stomach is responsible for churning (similar to chewing, but more dimensions of contraction affecting the food and breaking down), hydrolysis, and storing of food. The goal in the stomach is for the bolus to be a chyme, which is a more fluid type of substance. Moving on, the chyme will go into the small intestines, which is responsible for hydrolysis, and absorption of nutrients. Next, in the large intestine, absorption (not nutrients, more like water, ions, or vitamin K) takes place. Lastly, food is passed to the rectum. The rectum serves as a storage until it is time to expel the food through the anus through expulsion.
- Nutrient absorption begins when food enters the small intestine as a chyme. This occurs through the mucosal aspect of the lumen, which is covered in projections that resemble fingers and are known as villi. Microvilli, a type of microscopic hair-like structure found in the vili, increase each cell's surface area and promote improved nutrient absorption. Carbohydrates, lipids, and proteins are among the nutrients that are absorbed in the small intestine.