1. How does the food change in consistency and form?
- Chewing breaks down food into smaller pieces, forming a semi-solid paste called bolus. Saliva mixes with the food, starting the chemical digestion of carbohydrates with the enzyme amylase.
- The bolus is mixed with gastric juices, turning it into a liquid mixture called chyme. The stomach's acidic environment and enzymes further break down proteins.
- Chyme is mixed with bile from the liver and digestive enzymes from the pancreas. This process breaks down fats, proteins, and carbohydrates into their smaller components. The consistency becomes more fluid, facilitating nutrient absorption.
2. How could the body absorb the nutrients from the foods we eat?
- The inner walls are lined with tiny, finger-like projections called villi and microvilli, which increase the surface area for absorption. Nutrients like glucose, amino acids, and fatty acids are absorbed through these structures.
- Water-soluble nutrients (e.g., glucose, amino acids) enter the bloodstream directly, while fat-soluble nutrients (e.g., fatty acids, vitamins A, D, E, K) are absorbed into the lymphatic system before entering the bloodstream.
- Once in the bloodstream, nutrients are transported to cells throughout the body. Carrier proteins help move these nutrients across cell membranes to be used for energy, growth, and repair.