1. How does the food change in consistency and form?
Food changes in consistency and form through both mechanical and chemical digestion, which work together to break it down into smaller, absorbable components.
- Mechanical Digestion: The process starts in the mouth when food is chewed. Teeth grind the food into smaller pieces, increasing its surface area for easier chemical digestion. The tongue helps mix the food with saliva, forming a soft, moist bolus that is easier to swallow.
- Chemical Digestion: As the bolus mixes with saliva, the enzyme salivary amylase begins to break down starches into simpler sugars. Once the food is swallowed, it moves to the stomach, where stomach acids and enzymes like pepsin continue to chemically digest proteins. The stomach muscles churn the food, mixing it with digestive juices and transforming it into a semifluid substance called chyme.
- Further Breakdown in the Small Intestine: Chyme moves into the small intestine, where bile from the liver and enzymes from the pancreas further break down fats, proteins, and carbohydrates into their simplest forms—such as amino acids, fatty acids, and sugars—so they can be absorbed into the bloodstream.
In short, food changes from solid chunks to a liquid-like form, becoming progressively more broken down as it moves through the digestive system. This allows nutrients to be absorbed efficiently.
2. How could the body absorb the nutrients from the foods we eat?
The body absorbs nutrients from food through different transport processes in the small intestine:
- Active Transport: Nutrients like glucose and amino acids are absorbed with the help of energy (ATP), moving from the intestine into cells against a concentration gradient.
- Diffusion: Lipids (fats) are absorbed through simple diffusion, moving from the intestine into lymph vessels called lacteals, which then transport them into the bloodstream.
- Osmosis: Water is absorbed by osmosis, moving passively from the intestine into the bloodstream, balancing hydration.
- Pinocytosis: Larger molecules, like some proteins, are absorbed by a process where cells engulf them in small vesicles.
These processes ensure efficient nutrient absorption for the body’s needs.