1. The food undergoes mechanical and chemical digestion of both the mouth and the stomach which change its consistency and form, making it easier for our body to absorb and utilize. Once the food enters the mouth, it undergoes mechanical digestion through chewing. The salivary gland is responsible for the chemical digestion inside the mouth by secreting salivary amylase, which helps break down starch into smaller molecules, and lingual lipase, which is activated in the stomach that helps break down dietary triglycerides or fats and oils. The food changes into bolus (soft solid), making it easier to be swallowed. Inside the stomach, the food is mechanically digested by the peristaltic contractions of the smooth muscles. These contractions are aided by gastric juice, converting the bolus into chyme (liquid).
2. Once the food is digested, the absorption of nutrients is then facilitated by the small intestine. The nutrients are absorbed through different processes: simple diffusion, facilitated diffusion, osmosis, and active transport. Electrolytes and amino acids are absorbed through diffusion or active transport, monosaccharides through facilitated diffusion and active transport, dietary lipids and vitamins through simple diffusion, and water through osmosis.