1. How does the food change in consistency and form?
The consistency and form of food change at every stage of the digestive process. In the mouth, food is broken into smaller pieces through chewing, while saliva softens it and starts breaking down starches with enzymes like amylase. Once swallowed, the food passes through the esophagus and enters the stomach, where it is mixed with gastric juices that contain hydrochloric acid and enzymes like pepsin. These substances break down proteins and turn the food into a semi-liquid form called chyme.
From the stomach, the chyme moves into the small intestine, where it is mixed with bile from the liver and digestive enzymes from the pancreas. These substances help emulsify fats and further break down carbohydrates, proteins, and fats into their simplest components. By the time the food reaches the end of the small intestine, it has been transformed into a liquid mixture of nutrients, water, and waste.
2. How could the body absorb the nutrients from the foods we eat?
The body absorbs nutrients mainly in the small intestine, which is designed for efficient nutrient uptake. The walls of the small intestine are lined with villi, tiny finger-like projections that increase the surface area available for absorption. Each villus is covered with even smaller structures called microvilli, forming a brush border that further enhances nutrient absorption.
As the digested food passes through the small intestine, nutrients like glucose, amino acids, fatty acids, vitamins, and minerals are absorbed into the bloodstream or lymphatic system. Carbohydrates are broken down into simple sugars like glucose, which enter the blood via active transport. Proteins are broken into amino acids and absorbed similarly, while fats are emulsified into smaller droplets and absorbed into the lymphatic system as chylomicrons. The absorbed nutrients are then transported throughout the body via the blood or lymph. Glucose provides energy, amino acids repair and build tissues, and fatty acids contribute to cell membranes and energy storage. This coordinated process ensures the body gets the essential nutrients it needs for growth, repair, and overall health.