Digestion

• Digestive system


  • Digestion; organ; balanced diet; large and small intestine; oesophagus; stomach; pancreas, liver and gall bladder
• Why do we need digestion?

  Essential food components can be absorbed into our blood
• Mechanical digestion


  The physical breakdown of food e.g. chewing food using teeth, churning food in the stomach and peristalsis. No chemical bonds are broken, but mechanical digestion creates a larger surface area for enzymes to work on.
• Balanced diet


  Contains all the food groups (vitamins, minerals, protein, fat, carbohydrates, fibre and water) in the correct proportions
• Chemical digestion


  Involves the secretions of enzymes throughout the alimentary canal. These enzymes break the chemical bonds that hold food particles together to allow them to be broken down into small soluble molecules.
• Enzyme


  A molecule that speeds up the break down of food (but is not changed itself)

  
• Why is fat essential to the human body?

  Insulation, protects organs
• 3 main classes of enzymes

  • Carbohydrases (break down carbohydrates such as starch)
  • Proteases (break down proteins)
  • Lipases (break down lipids)
• Villi


  Tiny finger-like projections lining the wall of the small intestine
• Digestive enzymes


  Break down large food molecules into smaller food molecules that are small enough to pass into the blood and be transported to the cells of the rest of the body

  
• What can happen if we over eat?

  Gain weight, if this happens a lot can lead to obesity
• Digestive system as a production line

  1. Food capture

  2. Ingestion

  3. Physical digestion

  4. Chemical and physical digestion

  5. Chemical digestion and absorption of useful foods

  6. Reclaiming water

  7. Egestion
• Digestion overview

  1. Ingestion

  2. Digestion

  3. Absorption

  4. Egestion
• Bile


  A chemical that breaks down large fat droplets into small fat droplets (emulsification)
• Mouth


  1. Chewing mechanically digests food

  2. Enzymes in saliva chemically digest food
• Bile is alkaline


  It neutralises the stomach acid as food passes into the small intestine
• Villi


  • Increase the surface area of the small intestine
  • Increase the speed of diffusion
• Neutralising stomach acid


  Ensures enzymes in the small intestine are at their optimum (best) pH

  
• Oesophagus


  Muscles contract in waves (peristalsis) to push food down to the stomach
• Small intestine


  • Large surface area
  • Thin - usually single cell thick
  • Increased blood supply
• Parts of the alimentary canal

  • Mouth
  • Oesophagus/Gullet
  • Stomach
  • Small Intestine
  • Large Intestine
  • Rectum
  • Anus
• Parts of the digestive system


  • Mouth
  • Stomach
  • Small intestine
  • Large intestine
  • Oesophagus

  
• Crohn's disease


  Disease that mainly attacks the intestine and can result in severe diarrhoea, cramps and tiredness
• Stomach


  1. Enzymes chemically digest food

  2. Acid provides optimum pH for enzymes and kills bacteria
• Peristalsis


  Waves of muscle contractions that moves food along the gut
• Enzymes found in the small intestine


  • Protease enzymes (digest protein into amino acids)
  • Carbohydrase enzymes (eg. amylase, digest carbohydrates into glucose)
  • Lipase enzymes (digest fats/lipids into 3 fatty acids and 1 glycerol)

  
• Food moves through the alimentary canal


  By gravity and muscle contractions
• Small intestine


  Digested food passes into the blood to be carried around the body
• How does the food get into your blood?


  The digestion process
• Swallowing


  Tongue pushes food into the top of the oesophagus
• Digestion is the mechanical and chemical breakdown of food. It converts large insoluble molecules into small soluble molecules, which can be absorbed into the blood.
• Liver


  Makes bile which emulsifies fat droplets
• Mechanical digestion creates a larger surface area for enzymes to work on.
• Strong acid


  Kills bacteria in the stomach
• Digestive enzymes are catalysing the breakdown of large insoluble molecules into small soluble molecules which can be absorbed into the blood. Process is known as chemical digestion.
• Digestion in the mouth

  1. Mechanical digestion by chewing

  2. Amylase breaks down starch into maltose
• Gall bladder


  Stores bile which is then released into the small intestine
• Water


  Is absorbed into the blood from the large intestine
• The function of the colon is to absorb as much remaining water as possible, leaving solid waste called faeces, which is stored in the rectum, before it passes out of the anus.
• Faeces


  Are stored in the rectum