1. How does the food change in consistency and form?
Food undergoes several transformations in both consistency and form as it travels through the gastrointestinal tract:
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Oral Cavity: Mastication physically breaks food into smaller pieces, while saliva enzymes like amylase initiate hydrolysis, the chemical breakdown of starch into simpler sugars. This forms a soft, manageable sphere called a bolus, which is easy to swallow
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Stomach: The bolus enters the stomach, where it is churned and exposed to gastric juices containing hydrochloric acid and enzymes like pepsin. These processes transform the bolus into a semi-liquid substance called chyme
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Small Intestine: The chyme is mixed with bile (for fat emulsification) and pancreatic enzymes, which complete the digestion of carbohydrates, proteins, and fats. This breaks the chyme into absorbable molecules, such as glucose, amino acids, and fatty acids. The remaining residues move on to the large intestine
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Large Intestine: Non-nutritive residues are compacted as water and electrolytes are absorbed, forming solid feces
2. How could the body absorb nutrients from the foods we eat?
Nutrient absorption is primarily facilitated in the small intestine, with some processes occurring in the large intestine:
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Enzymatic Hydrolysis and Breakdown: In the small intestine, enzymes break complex food molecules into simpler forms—carbohydrates into glucose, proteins into amino acids, and fats into fatty acids and glycerol. These molecules are then absorbed through the intestinal walls.
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Intestinal Absorption: The small intestine's mucosa lining is equipped with villi and microvilli, which greatly increase the surface area for absorption. Nutrients pass into capillaries or lacteals.
- Additional Absorption: The large intestine absorbs water, certain ions, and vitamins like K. Although less nutrient absorption occurs here, it plays a crucial role in hydration and mineral balance.