Digestive System

• Digestive system


  An organ system comprised of organs with the major function to convert food into simpler, absorbable nutriments to keep the body functioning and healthy
• Digestive system in humans

  • Fundamentally comprised of the gastrointestinal tract
• Digestive system phases

  1. Ingestion

  2. Movement

  3. Mechanical and chemical digestion

  4. Absorption

  5. Elimination
• Ingestion

  The process of taking food into the mouth
• Mechanical digestion

  • Chew
  • Tear
  • Grind
  • Mash
  • Mix
• Chemical digestion


  Breaking larger molecules into smaller molecules through enzymatic reactions
• Enzymatic reactions to improve digestion of

  • Carbohydrates
  • Proteins
  • Lipids
• Absorption


  The process of moving nutrients, water, and electrolytes from the lumen of the small intestine into the cells and then into the blood
• Elimination


  Molecules that are not absorbed and undigested are eliminated and pass out of your body as wastes through anus
• Gastrointestinal (GI) tract


  • Tube within a tube
  • Direct link/path between organs
• Structures of the GI tract

  • Mouth
  • Pharynx
  • Esophagus
  • Stomach
  • Small intestine
  • Large Intestine
  • Rectum
• Mouth

  • Teeth mechanically break down food
  • Tongue mixes food with saliva (contains amylase, which helps break down starch)
  • Epiglottis, flap-like structure, prevents food entry (located in Pharynx)
• Esophagus

  • Approximately 20 cm long
  • Secretes mucus
  • Moves food from throat to stomach via peristalsis (muscle movement)
  • Causes heartburn if stomach acid enters
• Stomach


  • J-shaped muscular bag for food storage and digestion
  • Mixes food with Digestive Juices that contain enzymes to break down Proteins and Lipids
  • Kills bacteria with acid (HCl)
  • Chyme (food) found in stomach
• Small intestine

  • 7 meters long
  • Lining features finger-like villi for increased surface area
  • Villi covered in microvilli for increased absorption
• Large intestine

  • 1.5 meters long
  • Accepts what small intestines don't absorb
  • Rectum (short term storage which holds feces before it is expelled)
  • Bacterial digestion: Ferment carbohydrates, Absorb more water, Concentrate wastes
• Liver

  • Directly affects digestion by producing bile (helps digest fat)
  • Filters out toxins and waste including drugs, alcohol and poisons
• Gallbladder


  • Stores bile from the liver, releases it into the small intestine
  • Fatty diets can cause gallstones
• Pancreas


  • Produces digestive enzymes to digest fats, carbohydrates and proteins
  • Regulates blood sugar by producing insulin