1. How does the food change in consistency and form?
- The first change happens in the mouth. Mastication breaks down food into smaller pieces (mechanical digestion). At the same time, our saliva, containing salivary amylase begins the chemical digestion (carbohydrates). This entire process turns the food into a bolus (a ball-like structure made of food that has been chewed and mixed with saliva).
- The bolus then travels down to the stomach, where muscles churn and mix the food with gastric juices. This gastric juice breaks down proteins (chemical digestion). After being mixed with gastric juice, the bolus turns into chyme, a semi-fluid mass or partially digested food. Chyme enters the small intestines where pancreatic enzymes and bile break down carbohydrates, proteins, and fats into simpler molecules for absorption.
2. How does the food change in consistency and form?
- It is lined with villi and microvilli, increasing the surface area for absorption. Nutrients are absorbed through the villi and directed into the bloodstream by epithelial cells that line the villi. In the center of each villus are capillaries and lacteals. Capillaries help absorb water-soluble nutrients, while absorb fat-soluble nutrients. Absorption involves several processes for nutrient transfer, ion transport. Under passive transport, nutrient absorption requires osmosis, simple diffusion, and facilitated diffusion.