The Digestive System: How Your Body Processes Food From Mouth to Intestines - Part 3

stream. People without appendixes have slightly higher rates of certain infections and may take longer to recover gut bacteria after disturbances. While not essential for survival, the appendix contributes to optimal digestive health. Can stress really cause stomach ulcers? Stress alone doesn't cause ulcers, but it contributes to their development and impairs healing. Most ulcers result from Helicobacter pylori bacteria or NSAIDs. However, stress suppresses immune function, potentially allowing H. pylori overgrowth. Stress also increases stomach acid production, decreases protective mucus, and reduces blood flow to the stomach lining. These changes make the stomach more vulnerable to ulcer formation and slower to heal existing ulcers. Managing stress remains important for digestive health even though bacteria, not stress, is the primary ulcer cause. Why do I feel tired after eating a large meal? Post-meal fatigue has several causes. Large meals trigger substantial blood flow diversion to digestive organs, potentially reducing brain blood flow. Carbohydrate-rich meals cause insulin release, which promotes tryptophan uptake in the brain, leading to serotonin production and sleepiness. The parasympathetic nervous system dominates during digestion, promoting the "rest and digest" state. Overeating requires extensive energy for digestion, contributing to fatigue. Certain foods naturally contain sleep-promoting compounds. This normal response becomes problematic only when extreme or interfering with daily activities. What determines how fast or slow my metabolism is? Metabolic rate depends on multiple factors beyond digestive function. Basal metabolic rate—calories burned at rest—accounts for 60-75% of total energy expenditure. Factors include body composition (muscle burns more calories than fat), age (metabolism slows 2-3% per decade after 30), sex (men typically have higher rates), genetics, thyroid hormone levels, and physical activity. The thermic effect of food—energy required for digestion—uses about 10% of calories consumed. While you can't dramatically change your baseline metabolism, building muscle mass and staying active optimize metabolic function. The digestive system represents a remarkable biological processing plant, transforming the incredible variety of foods humans consume into the universal building blocks of life. From the first bite to final elimination, this system demonstrates exquisite coordination of mechanical, chemical, neural, and hormonal mechanisms. Understanding your digestive system empowers you to make choices supporting its optimal function, ensuring efficient nutrient extraction and contributing to overall health and well-being throughout your lifetime.