Human nutrition

• Mouth


  Contains teeth used for mechanical Digestion, an area where food is mixed with salivary amylase & where ingestion takes place
• Salivary glands

  Produce saliva, which contains amylase and helps food slide down the oesophagus
• Oesophagus


  Tube-shaped organ that uses peristalsis (circular muscle contract and relax) to transport food from mouth to stomach
• Stomach

  Has pepsin (a protease that works best in acidic conditions) to break down proteins into amino acids and kills bacteria with hydrochloric acid. They also have elastic walls.
• Small intestine


  • Tube-shaped organ composed of two parts: Duodenum and Ileum
• Duodenum


  Fats: emulsified by bile

  Lipase -> fatty acids and glycerol.

  Amylase and trypsin break down starch and protein
• Ileum


  Maltase breaks down maltose to glucose. This is where absorption takes place, adapted by having villi and microvilli.
• Pancreas


  Produces amylase, trypsin (a protease that works best in alkaline conditions), and lipase.
• Liver


  Produces bile (emulsifies fats, neutralises acidic fat molecules), deamination, and makes urea to be sent to the kidney. Also, it is the site of the breakdown of alcohol and other toxins.
• Gall bladder


  Stores bile from the liver
• Large intestine

  • Tube-shaped organ composed of two parts: Colon and Rectum
• Colon


  Organ for absorption of minerals and vitamins and reabsorbing water from waste to maintain the body's water levels
• Rectum


  Where faeces are temporarily stored
• Anus


  A ring of muscle that controls when faeces is released.
• Amylase


  Breaks down starch into maltose; it is produced in the pancreas (but also in the salivary gland)
• Maltase


  Maltose into glucose in the membrane of the epithelium lining in small intestines
• Protease


  Proteins into peptides (pepsin-acidic)

  Amino acids (trypsin)
• Lipase


  Breaks down lipids into fatty acids and glycerol, produced by the pancreas
• Hydrochloric acid in gastric juice

  • Denaturing enzymes in harmful microorganisms
  • Giving the optimum pH for pepsin activity
  • Kills pathogens
• Bile


  An alkaline mixture that neutralises the acid mixture of food and gastric juices entering the duodenum from the stomach to provide a suitable pH for enzyme action
• Small intestine


  Region for absorption of digested food
• Small intestine

  • Folded into many villi, increasing the surface area for absorption
  • One villus will have tiny folds on the cells on its outside called microvilli
• Epithelium

  One cell thick, allowing efficient diffusion of nutrients
• A large surface area means more absorption of nutrients can happen
• Lacteals


  Absorbs fatty acid and glycerol
• Capillaries


  Provide a good blood supply and a steep concentration gradient
• Most water is absorbed from the small intestine, and some from the colon (large intestine)
• Incisors


  • Chisel-shaped for biting and cutting
• Canines

  • Pointed for tearing, holding and biting
• Premolars and molars

  • Larger, flat surfaces with ridges at the edges for chewing and grinding up food