(7) human nutrition

• Deficiency of vitamin C

  Scurvy, bleeding under skin, poor wound healing, swollen bleeding gums
• Deficiency of vitamin D

  Rickets, soft deformed bones, calcium not deposited properly
• Ingestion


  Taking of substances into the body
• Digestion


  Breakdown of food
• Absorption


  Movement of nutrients from intestines into blood
• Assimilation


  Uptake and use of nutrients by cells
• Egestion


  Removal of undigested food from body as faeces
• Physical digestion


  Breakdown of food into smaller pieces without chemical change to the food molecules
• Teeth


  • Incisors: bite and cut
  • Canine: tear and rip
  • Pre molars: grind
  • Molars: chew
• Chemical digestion


  Breakdown of large insoluble molecules into small soluble molecules
• Starch digestion


  1. Amylase produced by salivary glands/pancreas breakdown starch into maltose

  2. Maltase produced by ileum breakdown maltose into glucose
• Fat and oil digestion

  Lipase produced by pancreas breakdown fats and oils into fatty acids and glycerol
• Protein digestion


  1. Pepsin produced by stomach breakdown protein into polypeptide

  2. Trypsin produced by pancreas breakdown polypeptide into dipeptide

  3. Erepsin produced by ileum breakdown dipeptide into amino acid
• Stomach


  • Contracts, churning food
  • Has hydrochloric acid (in gastric juice) which kills harmful microorganisms and prepares acidic conditions for pepsin
  • Mucus protects stomach wall from acid
• Bile


  • Produced by liver, stored by gall bladder, used by duodenum
  • Emulsifies fats, higher surface area for chemical digestion
  • Alkaline mixture that neutralises acidic mixture of food and gastric juices (provides suitable pH for enzymes)
• Villi


  • Epithelium is 1 cell thick with microvilli, shorter diffusion distance
  • A lot of villi, bigger surface area, more absorption
  • Lacteal absorbs fatty acids and glycerol
  • Blood capillary absorbs glucose and amino acid
• Nutrients absorbed in small intestine

  • Glucose
  • Fatty acid and glycerol
  • Amino acid
  • Vitamins
  • Water
• Large intestine


  • Colon absorbs water
  • Rectum stores faeces
  • Anus empties rectum