Digestive System

• Mechanical Digestion


  Breaking up food into smaller pieces to increase the surface area to volume ratio of the food so it can be chemically digested more efficiently
• Chemical Digestion


  Changes what the food is made of, it's a chemical reaction. Involves digestion by enzymes. Takes molecules and breaks it into a different kind of molecule. Chemically alters the substances that are in food.
• The Mouth


  • Includes the teeth and tongue
  • Main purpose is to mechanically digest food
  • Chewing into smaller pieces, creates a greater surface area to volume ratio which makes chemical digestion more efficient
  • Chewing mixes food with saliva to help swallow and break down
• The Oesophagus


  • Goes from the mouth to the stomach
  • Food gets pushes down the oesophagus by muscle contractions
• The Stomach


  • Main purpose is to mix the food with pepsin
  • Chemically digest proteins into amino acids
  • Very acidic
  • Churns the food and releases chyme into the small intestine
• The Small Intestine


  • Helps with chemical digestion and absorption
  • Produces intestinal juice and continues the chemical digestion of starch and proteins
  • Initiates chemical digestion of lipids
  • Large surface area so more can be absorbed
  • The 3 parts are: duodenum, jejunum, ileum
• The Pancreas


  • Neutralize the acidity from the stomach
  • Continues to digest
• The Liver


  • Filters the blood
  • Creates bile
• The Gallbladder


  • Bile is stored in the gallbladder
  • The bile mixes with the food which help emulsify the lipids, creating a greater surface area
• The Large Intestine


  • Absorbs water
  • Helps faeces to be stored in the rectum
  • Contains lots of bacteria
• Macronutrients

  • Carbohydrates - Source of immediate energy
  • Lipids - Energy storage
  • Proteins - Structure the cell, cell receptors, enzyme
• Micronutrients

  • Vitamins - Make enzymes
  • Minerals - Structural components of organisms
• Lipids (fats and oils) are broken down


  Broken into fatty acids and glycerol by enzymes called lipases
• Complex Carbohydrates are broken down


  Broken into simple sugars by an enzyme called amylases
• Proteins are broken down


  Broken into amino acids by enzymes called proteases
• The large intestine absorbs water and forms feces.
• The small intestine is where most nutrient absorption occurs through villi and microvilli.
• The liver produces bile salts that emulsify fats, stores glucose as glycogen, detoxifies substances, and makes clotting factors.
• Gallbladder stores bile produced by the liver until needed.