1. How does the food change in consistency and form?
The food we eat undergoes significant changes in consistency and form as it moves through the digestive system. In the mouth, mechanical digestion (chewing) breaks food into smaller pieces, while salivary enzymes begin chemical digestion, forming a soft, moist mass called a bolus. The bolus travels down the esophagus into the stomach, where gastric juices and enzymes break it down further into a semi-liquid mixture called chyme. In the small intestine, chyme mixes with bile and pancreatic enzymes, breaking down fats, proteins, and carbohydrates, while nutrients and water are absorbed by the villi. In the large intestine, water absorption continues, hardening the chyme into feces, which are stored in the rectum before being expelled. Feces are solid or semi-solid waste composed of undigested food remnants and residual water.
2. How could the body absorb the nutrients from the foods we eat?
The body absorbs nutrients from food through a complex process beginning with digestion in the mouth, where enzymes start breaking down carbohydrates into simpler sugars. In the stomach, proteins are broken into peptides by gastric juices. Most nutrient absorption occurs in the small intestine, where bile and pancreatic enzymes break down carbohydrates, proteins, and fats into their simplest forms (glucose, amino acids, and fatty acids). The villi and microvilli in the small intestine absorb these nutrients into the bloodstream (for carbohydrates and proteins) or lymphatic system (for fats) for transport to the body. In the large intestine, remaining water and minerals are absorbed, completing the process.