Processes in the digestive system

• Ingestion

  1. Taking in food into the mouth and gastrointestinal tract

  2. Saliva release triggered

  3. Amylase in saliva digests starch and glycogen

  4. Propulsion of food down gastrointestinal tract

  5. Swallowing is voluntary propulsion

  6. Peristalsis is involuntary propulsion

  
• Digestion

  1. Mechanical digestion: Mastication, Churning, Segmentation

  2. Chemical digestion: Gastrin triggers stomach to produce pepsinogen, mucus, hydrochloric acid

  3. Digestion in small intestine: Bile emulsifies fats, Pancreatic juice contains amylases, proteases, lipases

  
• Mechanical digestion


  Physical breakdown of food without chemical reactions
• Chemical digestion


  Breakdown of food using chemical reactions

  
• Enzymes/Acids involved in chemical digestion

  • Gastrin
  • Hydrochloric acid
  • Pepsin
  • Mucus
  • Bile
  • Pancreatic juice
• Absorption

  1. Transport of digested food into bloodstream via intestinal capillaries and lacteals

  2. Absorption of specific molecules in gastrointestinal tract

  
• Intestinal villi and microvilli

  Increase surface area for absorption
• Assimilation

  1. Building up of complex substances after absorption

  2. Fatty acids used to form fats

  3. Amino acids used to form proteins

  4. Monosaccharides used to form polysaccharides

  5. Synthesis of essential compounds like hormones and enzymes
• Excretion

  1. Elimination of undigested food

  2. Feces contain indigestible materials, water, mucus, bacteria

  3. Peristalsis and mass movements in large intestine move feces to rectum

  4. Defecation reflex signals excretion
• The journey of food from mouth to anus involves 6 processes: ingestion, propulsion, digestion, absorption, assimilation, and excretion
• Each process has specific events for breaking down food, absorbing nutrients, and removing waste
• Organs of digestive system have specific functions related to the processes

  
• Food is broken down into smaller components for better absorption, then built back up for use by the body