1. How does the food change in consistency and form?
The change in the food's consistency begins in the mouth where it is broken physically broken down through mastication or chewing. Through this process, the food is broken down into smaller pieces. The resulting mass is called "bolus". Afterward, it is mixed with saliva, which will allow easier swallowing. Once it reaches the stomach, the gastric juices inside will begin to dissolve the food making its consistency semi-liquid. This semi-liquid form is called "chyme". By the time it reaches the small intestine, it is mostly in its liquid form with most of the nutrients already broken down. In the small intestine, the secretions from the pancreas and liver mixes with the chyme. These secretions contain enzymes which will completely breakdown the carbohydrates, fats, and proteins content of the chyme into their much simple forms that will allow the body to absorb. In the large intestine, the water is absorbed from the mass which will allow the remaining matter to solidify and turn into feces.
2. How could the body absorb the nutrients from the foods we eat?
The small intestine contains circular folds, villi, and microvilli, which all increases the surface area for easier absorption. As the food reaches the small intestine, it is mixed with the secretions of pancreas and liver which will allow the carbohydrates, fats, and proteins turn into monosaccharide, lipids, and amino acids, respectively. Because these nutrients are broken down into their more simple forms, the body, through the linings in the intestinal wall, easily absorbs them through the blood capillaries and lymphatic vessels.
Tortora, G. J., & Derrickson, B. (2017). Principles of anatomy & physiology (pp. 914-968). Fifteenth edition; Wiley Loose-Leaf Print Companion. Hoboken, New Jersey, John Wiley & Sons, Inc.