Food is energy source and source of building blocks

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• Food is energy source and source of building
  blocks
• Body changes chemical energy stored in food into
• Mechanical energy
• Heat energy
• Chemical energy
• How?
• By burning it
• Anything that burns needs oxygen
• Thats why we have to breathe intake of oxygen
• What do calories have to do with this process?
• They are the unit for energy and indicate how
  much energy we can get from digesting a
  particular food

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Organs of Digestive Tract

• Mouth
• Pharynx
• Esophagus
• Stomach
• Small Intestine
• Large Intestine
• Rectum
• Anus
• Accessory glands and organs
• Salivary glands
• Pancreas
• Liver

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Function of Digestion

• Digestion is necessary so that molecules are
  small enough to pass through cell membranes
• Converts large, insoluble polymers into small,
  soluble monomers.

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Types of Digestion

• Mechanical- makes smaller pieces of food by
  chewing and peristalsis. Increases surface area
  for enzyme activity
• Chemical- breaks chemical bonds to form new
  molecules e.g. starch into glucose

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• Mouth
• Mechanical digestion- increase surface area for
  enzymes activity
• Chemical digestion amylase in saliva begins
  digestion
• of starch (complex carbohydrate) into glucose
• Pharynx
• Junction of esophagus and trachea
• Epiglottis temporarily closes of airway as food
  is swallowed
• Esophagus
• Ringed by muscles which contract peristalsis
• Food is pushed down toward stomach

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• Stomach
• Gastric juices (HCl, pepsin) are secreted by
  glands in stomach lining digesting proteins
• Mechanical digestion turns bolus into an acidic
  liquid called chyme
• Stomach muscles contract and eventually force
  chyme into small intestine

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• Small Intestine
• Long (6m) and narrow (2.5cm) tube first section
  is duodenum
• In duodenum chyme gets mixed with digestive
  juices
• Bile produced in liver stored in gallbladder,
  emulsifies fat
• Pancreatic juices neutralize acidic chyme,
  contain enzymes that digest proteins,
  carbohydrates and lipids
• Villi in the small intestine are specialized for
  absorbing nutrients into circulatory and
  lymphatic system

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• Large Intestine (colon or bowel)
• Here bacteria produce vitamin K and several B
  vitamins
• Water is absorbed from undigestable food making
  it more solid water is recirculated
• Feces are stored in rectum until excreted