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• Digestive system


  Made up of the gastrointestinal tract and the liver, pancreas, and gallbladder

  
• Gastrointestinal tract


  A series of hollow organs joined in a long, twisting tube from the mouth to the anus
• Food taken in through the mouth is digested to extract nutrients and absorb energy, and the waste expelled as feces
• Organs that make up the digestive system

  • Mouth
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine
  • Rectum
  • Anus
  • Pancreas
  • Gallbladder
  • Liver

  
• Mouth


  Beginning of the digestive tract where digestion starts before eating, chewing food, and swallowing
• Esophagus


  Receives food from the mouth, uses peristalsis to deliver food to the stomach, has a lower esophageal sphincter to prevent reflux

  
• Stomach


  Hollow organ that holds food and mixes it with enzymes to break it down, then releases it into the small intestine
• Small intestine


  22-foot long muscular tube that further breaks down food using enzymes from the pancreas and bile from the liver, absorbs nutrients
• Duodenum


  First segment of the small intestine responsible for continuous breakdown of food
• Jejunum and ileum


  Lower segments of the small intestine mainly responsible for absorption of nutrients

  
• Pancreas


  Secretes digestive enzymes into the duodenum and insulin into the bloodstream
• Liver


  Processes the nutrients absorbed from the small intestine, secretes bile to aid in fat digestion
• Gallbladder


  Stores and concentrates bile from the liver, releases it into the duodenum to help digest fats
• Colon (large intestine)


  1. foot long muscular tube that connects the small intestine to the rectum, processes waste
• Rectum


  Straight 8-inch chamber that connects the colon to the anus, receives stool and signals the brain to initiate a bowel movement
• Anus


  1. inch long canal with sphincter muscles that allow control of stool elimination
• The digestive system consists of the gastrointestinal tract plus the accessory organs of digestion

  
• Digestion


  The breakdown of food into smaller and smaller components that can be absorbed and assimilated into the body
• Digestive processes


  • Ingestion
  • Propulsion
  • Mechanical/physical digestion
  • Chemical digestion
  • Absorption
  • Defecation

  
• Ingestion


  The entry of food into the alimentary canal through the mouth
• Stages of food processing

  • Ingestion
  • Digestion
  • Absorption
  • Elimination
• Digestion


  Breaking down food into nutrients that the body can use for energy, growth, and cell repair
• Pepsin


  An endopeptidase enzyme produced in the stomach that breaks down proteins into smaller peptides
• Protease


  An enzyme that catalyzes the breakdown of proteins into smaller polypeptides or amino acids by cleaving peptide bonds
• Salivary amylase


  An enzyme produced by the salivary glands that begins the breakdown of complex carbohydrates in the mouth
• Mechanical digestion


  Begins in the mouth as food is chewed
• Chemical digestion


  Begins in the mouth as food mixes with saliva containing amylase enzyme
• Digested food molecules are absorbed in the small intestine and carried in the bloodstream to where they are needed

  
• Chyme


  The pulpy acidic fluid that passes from the stomach to the small intestine, consisting of gastric juices and partly digested food
• Villi


  Finger-like projections that line the interior wall of the small intestine and absorb most of the nutrients

  
• Lacteals


  The lymphatic vessels of the small intestine that absorb digested fats
• Capillaries


  Microscopic blood vessels that connect the arterioles and venules, forming a capillary bed to absorb nutrients
• Large intestine


  Compacts liquid waste into solid waste (feces)
• Interstitial fluid


  Leaked fluid that bathes your body cells in nutrients
• Large intestine


  Compacts liquid waste into solid waste
• Passage of chyme from small intestine to large intestine

  1. Chyme passes from the small intestine through the ileocecal valve and into the cecum of the large intestine

  2. Any remaining nutrients and some water are absorbed as peristaltic waves move the chyme into the ascending and transverse colons

  3. Dehydration, combined with peristaltic waves, helps compact the chyme
• Chyme


  Pulpy acidic fluid which passes from the stomach to the small intestine, consisting of gastric juices and partly digested food
• Formation and movement of solid waste in the large intestine

  1. The solid waste formed is called feces

  2. It continues to move through the descending and sigmoid colons

  3. The large intestine temporarily stores the feces prior to elimination
• Defecation


  1. Contraction of rectal muscles

  2. Relaxation of the internal anal sphincter

  3. Initial contraction of the skeletal muscle of the external anal sphincter
• Defecation reflex


  Mostly involuntary, under the command of the autonomic nervous system, but the somatic nervous system also plays a role to control the timing of elimination