1. How does the food change in consistency and form?
Food is ingested through the mouth and is broken down mechanically (through mastication) and chemically (by salivary enzymes) to form a ball-like mixture of food and saliva called bolus. The bolus is swallowed and transported by the esophagus and enters the stomach, where the bolus is mixed with gastric juices to form a liquid mixture called chyme. Chyme then travels through the small intestine where most nutrients are absorbed, then travels through the large intestine where water is absorbed, leaving behind a solid mass of waste called feces which is expelled from the body through defecation.
2. How could the body absorb the nutrients from the foods we eat?
The body is able to absorb nutrients from food by breaking it down through the digestive processes in the digestive system. The process starts from the mouth where food is broken down by mechanical and chemical digestion. Here, starch is broken down by salivary amylase present in the mouth. The food is transported by the esophagus to the stomach, where carbohydrates, proteins, and lipids are broken down by gastric juices in the stomach with the help of enzymes from the liver and pancreas. These broken-down molecules are then absorbed by the small intestine where small finger-like projections called villi are present to increase surface area, allowing efficient absorption of nutrients into the bloodstream where these nutrients are transported around the body. Some remaining essential molecules are absorbed by the large intestine, and the unwanted molecules are then eliminated from the body.