N3 Anatomy and Physiology AY 2024-2025

How does the food change in consistency and form?

• Food starts as solid or semi-solid when consumed. In the mouth, it undergoes mechanical breakdown (chewing) and chemical breakdown through enzymatic action (hydrolysis). This process reduces the food into smaller, more manageable particles, forming a cohesive mass called a bolus. After swallowing, the bolus moves down the esophagus into the stomach, where intense churning and additional enzymatic digestion turn it into a semi-liquid substance known as chyme. This transformation continues as the chyme progresses through the small intestine, where it is further broken down into its molecular components for nutrient absorption. Finally, any remaining undigested material is processed in the large intestine and expelled as waste.

How could the body absorb the nutrients from the foods we eat?

• Nutrients are absorbed in the small intestine, where the chyme is exposed to digestive enzymes and bile, further breaking it down into basic molecules such as amino acids, glucose, and fatty acids. These molecules are then absorbed through the villi and microvilli lining the intestinal walls, increasing the surface area for maximum nutrient uptake. From there, nutrients enter the bloodstream or lymphatic system to be transported to cells throughout the body. Water, electrolytes, and certain vitamins are also absorbed in the large intestine, ensuring efficient utilization of ingested materials.