1. How does the food change in consistency and form?
When food is eaten and digested, it undergoes significant changes in consistency and form through mechanical and chemical processes. The transformation begins in the mouth, where chewing breaks food into smaller pieces, mixing it with saliva to form a soft, pliable mass called a bolus. Saliva contains enzymes, such as amylase, which start breaking down carbohydrates into simpler sugars. Once swallowed, the bolus travels to the stomach, where it is mixed with gastric juices, including acid and enzymes like pepsin, which break down proteins. This process turns the food into a semi-liquid substance called chyme. The chyme then moves into the small intestine, where it is further broken down by bile from the liver and digestive enzymes from the pancreas. These substances emulsify fats and reduce complex nutrients into their simplest forms—amino acids, fatty acids, and simple sugars—for absorption. Finally, the undigested material passes into the large intestine, where water is reabsorbed, and the remaining material is compacted into solid waste. Through this intricate process, food transforms from a solid to a variety of liquid and semi-solid states, enabling the body to extract nutrients and energy.
2. How could the body absorb the nutrients from the foods we eat?
The body absorbs nutrients from food through the digestive system, primarily in the small intestine, after breaking the food down into its simplest forms. Digestion begins in the mouth, where enzymes in saliva start breaking down carbohydrates. In the stomach, acids and enzymes further digest proteins and mix the food into a liquid-like substance called chyme. As chyme enters the small intestine, bile from the liver emulsifies fats, and enzymes from the pancreas break down proteins, fats, and carbohydrates into their basic components: amino acids, fatty acids, and simple sugars. The inner walls of the small intestine are lined with tiny finger-like structures called villi, which are covered with even smaller structures called microvilli, creating a large surface area for absorption. Nutrients pass through these structures into the bloodstream or lymphatic system: water-soluble nutrients like amino acids and sugars enter the bloodstream, while fat-soluble nutrients like fatty acids and vitamins are absorbed into the lymphatic system. From there, the nutrients are transported to cells throughout the body to provide energy, support growth, and maintain vital functions. This efficient system ensures the body can utilize the essential components of the food we consume.