How does the food change in consistency and form?
- First, mastication breaks food into smaller pieces, forming a soft, moist mass called a bolus. Additionally, salivary glands secrete salivary amylase, which breaks down starch into simple sugars in the mouth. Then, after the bolus moves down into the esophagus, it enters the stomach and mixes with gastric juices. These juices contain enzymes and acids that break the food into a thick, semi-liquid form called chyme. It then enters the small intestine, wherein enzymes from the pancreas and bile from the liver further break down the chyme into nutrients the body can use. These help break down fats, proteins, and carbohydrates, making it easier for the body to absorb nutrients. Lastly, the large intestine absorbs water, electrolytes, and some vitamins, forming a waste called feces.
How could the body absorb the nutrients from the foods we eat?
- Absorption happens in three digestive system organs: In the stomach, small amounts of water, alcohol, and some drugs like aspirin are absorbed. However, most nutrients are not absorbed here because of the impermeability of the stomach walls. Most nutrients are absorbed in the small intestine. Fats are broken down into fatty acids, absorbed into cells, and transported through the lymphatic system. Moreover, carbohydrates are digested into simple sugars and absorbed into the bloodstream. Additionally, proteins are broken into amino acids and absorbed into the bloodstream. Lastly, fat-soluble vitamins are absorbed along with fats, and water-soluble vitamins and minerals are absorbed through diffusion or specific transport mechanisms. These nutrients are transported to the liver for processing or sent directly to cells via the bloodstream and lymphatic system. On the other hand, in the large intestine, water, electrolytes, and vitamins are absorbed. The remaining material solidifies into feces, ready for elimination.