Digestive System

• Nucleus


  An organelle
• Organ system


  Organs work together
• How multicellular organisms are organised

  1. Tissues

  2. Organs

  3. Organ systems
• Muscular tissue


  • Can contract to bring about movement
• Glandular tissue


  • Contains secretory cells that can produce and release substances such as hormones and enzymes
• Epithelial tissue


  • Covers the outside of your body as well as your internal organs
• Muscular tissue contracts
• Glandular tissue produces and releases hormones and enzymes
• Epithelial tissue covers the outside and internal organs
• Organ


  The stomach
• Why the stomach has each tissue type

  1. Muscular tissue to churn the food and digestive juices

  2. Glandular tissue to produce and release digestive chemicals

  3. Epithelial tissue to cover the inside and outside
• Digestion


  Breaking up large, insoluble molecules into smaller, soluble molecules
• Why we need to digest food

  The nutrients in food need to be broken down into smaller molecules so they can be absorbed into the bloodstream
• How digestive enzymes work

  Break the bonds between nutrient molecules so they are small enough to be absorbed
• Why chemically digest food

  To break down large, insoluble molecules into smaller, soluble ones
• Nutrients in food


  • Carbohydrates
  • Proteins
  • Lipids
  • Vitamins
  • Minerals
• Carbohydrates


  Provide fuel for other reactions, made up of carbon, hydrogen and oxygen, consist of simple and complex sugars
• Carbohydrate digestion


  Carbohydrase enzyme breaks the bonds between sugar molecules in carbohydrate chains
• Proteins


  Used for building cells and tissues, have a wide range of biological roles, made up of amino acids
• Protein digestion


  Proteases break proteins into smaller amino acids in an acidic environment
• Lipids


  Fats and oils, efficient energy stores, important in cell membranes, hormones and nervous system, made up of fatty acids and glycerol, insoluble in water but soluble in ethanol
• Fat digestion


  Bile emulsifies fat into smaller droplets, lipase then breaks fat molecules into glycerol and fatty acids
• Digestive system summary


  1. Teeth physically break down food

  2. Salivary glands secrete saliva to start chemical digestion

  3. Food moves through oesophagus, stomach and intestines by muscle contractions

  4. Stomach chemically digests food

  5. Bile from liver/gallbladder emulsifies fats in small intestine

  6. Villi and microvilli in small intestine increase surface area for nutrient absorption into bloodstream
• Food tests


  • Starch
  • Fat
  • Glucose
  • Protein
  • Minerals
  • Vitamins
• Starch is found in wheat/bread. potatoes and bananas
• Starch is needed for energy since it is a good source of energy and to maintain a range of nutrients in our diets
• Fat is found in milk, meats and oils similar to proteins
• Fat is needed to give your body energy and support cell function
• Protein is found in different meats, milk and eggs
• Protein is needed to help your body repair cells and make new ones
• Minerals are found in cereals, bread, dairy and nuts.
• Minerals are needed to build strong bones and teeth
• Glucose is found in fruit, vegetables and honey
• Glucose is needed to fuel both aerobic and anaerobic cellular respiration
• Vitamins are found in meat, vegetables, fruit, bread, eggs
• Small intestine


  • Has lots of tiny folds which create a large surface area for absorbing nutrients
  • Has villi which are finger-like projections
  • Surface cells of the villi have microscopic projections called microvilli
  • Together, the villi and microvilli make the surface area of the small intestine huge
• Large surface area of small intestine

  Increases the number of nutrients which can be absorbed into the blood
• Villi


  • Have a good blood supply not far away
  • This shortens the diffusion distance and maintains a high concentration gradient which increases the rate of diffusion
• Food tests


  • Starch
  • Fat
  • (Sugar) Glucose
  • Protein
  • Minerals
  • Vitamins
  • Fibre
  • Water
• There is no food test for water. To keep healthy we should drink 8 glasses a day