- How does the food change in consistency and form?
Food changes in consistency and form as it moves through the digestive system. First, it begins in the mouth, where mechanical digestion occurs through chewing. Food is then broken down into smaller pieces. Salivary glands secrete saliva, which contains enzymes like salivary amylase and lingual lipase, which break down large macromolecules into simpler molecules. Once mixed with saliva, the food forms into a small mass called bolus, making it easier to swallow
Once swallowed, the food passes through the esophagus and reaches the stomach, where hydrochloric acid and pepsin further break down proteins into smaller peptides. The food is churned into a semi-liquid form called chyme. This moves into the small intestine, where it is mixed with bile and other enzymes—which help emulsify fats and further break down carbohydrates, proteins, and lipid. Nutrients are absorbed through the walls of the small intestine and into the bloodstream, leaving behind undigested material.
The remaining material enters the large intestine, where water is absorbed, turning it into solid waste. This moves into the rectum until defecation, during which it is expelled through the anus as feces. This removes unused and indigestible substances from the body.
- How could the body absorb the nutrients from the foods we eat?
In the digestive process, the absorption occurs mainly in the small intestine of the body. After food is broken down into its simplest molecules—amino acids, monosaccharides, and peptides—the nutrients are absorbed through the lining of the small intestine. This wall is covered with finger-like projections called villi, which increase the surface area for absorption.
Nutrients are absorbed through various means, including diffusion and facilitated diffusion, osmosis, and active transport. Water-soluble nutrients, such as glucose, amino acids, and vitamins B and C, are absorbed directly into the bloodstream by entering blood capillaries within the villi. Meanwhile, fat-soluble nutrients, like fatty acids, glycerol, and vitamins A, D, E, and K, are directed to lacteals, which are lymphatic vessels that transport them to the lymphatic system. As food material passes through the small intestine into the large intestine, some nutrients may still be absorbed before it is fully converted into waste.
Overall, this absorption process ensures that the body receives the essential nutrients needed for energy, growth, repair, and overall function.