1. How does the food change in consistency and form?
The food we eat changes in consistency and form beginning from the mouth, where it undergoes mechanical and chemical digestion. The teeth in our mouth grind the food into smaller pieces, while the salivary enzymes begin to break down the carbohydrates in the food, turning it into bolus. As the bolus is moved down the esophagus, it is introduced to a variety of juices, fluids, proteins and enzymes (e.g., gastric juices, hydrochloric acid, digestive enzymes, pancreatic juices) that all aid in churning and further chemical digestion of the ingested food into chyme. The semi-fluid pulp of digested food then enters the various sections of the small intestines, where the villi absorb its nutrients and water. This absorption of water is continued along the large intestines— at this point, the chyme has slowly hardened (from reduced water content) and begins to more closely resemble fecal matter. Once it reaches the rectum for defecation, the feces appear to be a solid or semi-solid waste. It appears to be solid from the undigested remains of our food and still contains a slight watery consistency for ease of release.
2. How could the body absorb the nutrients from the foods we eat?
Beginning from the mouth, our body begins its digestion (both mechanical and chemical) through the mouth. As the mouth breaks down food into smaller and more digestible pieces, it also releases salivary enzymes that break down the dietary fibers into absorbable carbohydrates by the bloodstream. Other major structures that aid in chemical digestion of food include the stomach, pancreas, and liver. They release substances that break down carbohydrates, fats, and proteins into more easily absorbable forms. Once the formed chyme enters the small intestine, the villi and microvilli are able to directly absorb these essential nutrients. These absorbed nutrients enter the bloodstream or lymphatic system to be transported into the various tissues of the body.