1. How does the food change in consistency and form?
Chewing breaks food into smaller pieces in the mouth, and saliva combines with food to create a bolus which is a soft, moist mass that is easier to swallow. After passing through the esophagus, the bolus is churned inside the stomach and combined with stomach acid and enzymes to create chyme, a semi-liquid substance. The small intestine then breaks down fats into smaller droplets and further breaks down proteins, carbohydrates, and fats into simpler molecules by combining chyme with bile and pancreatic juices. Finally, as water is absorbed, the large intestine solidifies any undigested material into feces.
2. How could the body absorb the nutrients from the foods we eat?
In the small intestine, proteins are broken down into amino acids, which are subsequently absorbed into the bloodstream, and carbohydrates are broken down into simple sugars, which are then absorbed into the bloodstream by microscopic finger-like structures called villi and microvilli. Bile emulsifies fats, breaks them down into fatty acids and glycerol, and then uses specialized structures called lacteals to absorb them into the lymphatic system. Finally, due to their solubility, vitamins and minerals are directly absorbed.