How the food changes consistency and form
In digestion, there are many processes that can happen to food for it to change consistency and form. First, there’s the mechanical breakdown (chewing) and enzyme-assisted breakdown (hydrolysis) of food within the mouth. Here, a bolus would then be shaped for swallowing, forming a sphere-like mass that has undergone the initial phases of digestion. Next, the bolus would be propelled by the esophagus into the stomach. In the stomach, there would be more dimensions of contractions to mechanically break down the bolus (churning). The churning movements would join together with enzymes and other gastric secretions for further digestion, which would be made possible by peristaltic movements in the stomach called mixing waves. With these mixing waves, there ends up a soupy liquid called chyme. The resulting chyme would then pass through the small intestine and large intestines, respectively, for hydrolysis and absorption. Here, the small intestine would mainly focus on both the hydrolysis and absorption of nutrients, whereas the large intestine would primarily absorb materials like water and ions. Afterward, the products from the hydrolysis and absorption that happened in the small and large intestines would go to the rectum for storage until it is released at an appropriate time. When it is finally time for the release, the products would be expelled as feces through the anus (Tortora & Derrickson, 2018).
How the body was able to absorb the nutrients from the foods we eat.
Primarily, there are two sites of absorption among the main organs of the digestive system: the small and large intestines (National Institute of Diabetes and Digestive and Kidney Diseases, 2013).
In the small intestine, the peristaltic movements help push chyme forward while mixing it with digestive juices from the pancreas, the liver, and the small intestine itself. Then, as the chyme passes through, the walls of the small intestine would absorb the digested nutrients and transfer them to the bloodstream. The blood would then be the one to distribute the nutrients to the other parts of the body (Tortora & Derrickson, 2018).
After finishing its course in the small intestine, what was left of the chyme as waste moves onto the large intestine to mainly finalize digestion. Here, the waste products, which are usually undigested parts of food and older cells from the lining of the gastrointestinal tract, would be pushed along the large intestine by its muscles. As the waste products progress along the large intestine, water, large molecules like ions and vitamin K, and any remaining nutrients would be absorbed. This process would change the liquid consistency of the waste products into feces. The feces would then be stored in the rectum until defecation (Tortora & Derrickson, 2018).
References:
National Institute of Diabetes and Digestive and Kidney Diseases. (2013). The digestive system and how it works. https://bit.ly/3tYVFBD
Tortora, G. J., & Derrickson, B. H. (2018). Principles of anatomy and physiology. John Wiley & Sons.