Final answer:
Digestion involves mechanical and chemical processes to break down food into nutrients, starting in the mouth and continuing in the stomach and small intestine. Some vegetable fragments may remain undigested due to their fibrous composition and appear in feces.
Step-by-step explanation:
Digestion refers to the process by which food is broken down into nutrients the body can use. This process involves two main types of digestion: mechanical digestion and chemical digestion. During mechanical digestion, food is physically broken down into smaller pieces, starting in the mouth where it is chewed by teeth, and continuing in the stomach where it is mixed and further broken down. In contrast, chemical digestion involves the breakdown of food at the molecular level into small nutrient molecules, facilitated by digestive enzymes and other substances.
Chemical digestion also begins in the mouth with enzymes in saliva starting to break down carbohydrates and continues in the stomach and mainly in the small intestine. The nutrient molecules produced by this process are then absorbed into the bloodstream. When you eat vegetables, some fragments may not be completely broken down, either mechanically or chemically, leading to their appearance in feces, often due to the tough, fibrous nature of certain vegetable matter that resists full digestion.