Chap 5 nutrition in humans

• Teeth : chewing increases the surface area of the food, which increases the rate of digestion and there is no new products formed.

  salivary glands : secrete ( an enzyme called salivary amylase ) saliva into the mouth ( chemical digestion takes place ) , new products are formed .
• Oesophagus: a narrow , muscular tube that passes through the chest and diaphragm. It connects the mouth and stomach, its walls consists of muscles ( expands and contracts )
• Stomach : has gastric glands which secrete gastric juice which contains hydrochloric acid ( ph 2 ) and protease ( proteins -> protease -> polypeptides). To kill bacteria (ph 2)and active protease.
• Small intestine : all digestion takes place c,p,f . 1) bile (physical digestion) 2) intestinal juice 3) pancreatic juice (enzymes and chemical digestion). absorbs water and nutrients from food.
• Liver : 1. Produces bile ( big fat droplet ->(bile)smaller fat droplet)( physical digestion, no new products are formed)2. Three blood vessels attached ( hepatic portal vein = blood from small intestine > liver , hepatic vein and hepatic artery).
• Large intestine: absorbs remaining water and mineral salts from undigested food.
• Gall bladder : stores bile produced by liver and releases it into small intestine. 1)emulsification will take place where bile physically breaks down fats into smaller fat droplets. 2)lipase will then be secreted into small intestine to break down fats into lipids into fatty acids and glycerol.
• Pancreas : 1. Produces digestive enzymes 2. Produces hormones. Produces pancreatic juice which contains digestive enzymes such as amylase ,lipase and protease . Secretes hormones such as insulin and glucagon, which helps to regulate blood sugar concentration in the body( influence wether a person has diabetes).
• Small intestine :

  Starch-> amylase -> maltose -> maltase -> glucose

  protein-> protease -> polypeptides - > protease -> amino acid

  fats-> lipase -> fatty acids + glycerol
• mouth :

  Starch-> amylase -> maltose
• stomach :

  protein -> protease-> polypeptide
• Assimilation : hepatic portal vein (contains blood high in glucose and amino acids )transports nutrients from small intestine to the liver.
• Excess amino acids are deaminated to form urea that is removed from the body in the urine.
• Liver produces bile which emulsifies fats . This increases the surface area of the fat molecules so they can be absorbed into the bloodstream.

  the liver helps to break down hormones.

  liver helps to regulate blood glucose concentration.
• high blood glucose concentration .

  • pancreas detects this and produces insulin .
  • insulin is transported in the blood to liver and muscle cells .
• low blood glucose concentration.

  • Pancreas detects this change and produces glucagon .
  • glucagon is transported in the blood to the liver.
• Type 1 diabetes

  • develops early in life
  • an inherited condition
• Type 2 diabetes

  • develops later in life (20 yrs )
  • develops when target cells, such as the muscle cells, do not respond well to insulin. this is called insulin resistance.
  • overweight people may have a higher chance of developing it .