The Digestive System

The Digestive System

1. The Human Digestive System

   • [Image: http://www.jewishhealthzone.com/wp-content/uploads/2011/11/Diagram-of-the-Digestive-System.jpg]
   • Mouth
     • Where food is mixed and chewed with saliva
     • Enzyme called Amylase begins the breakdown of starch
   • Oesophagus
     • tube that carries food to the stomach by muscular action
   • Liver
     • produces bile which helps to breakdown fats
   • Small Intestine
     • food molecules are absorbed into bloodstream
       • after final breakdown by enzymes
   • Large Intestine
     • passes water back into the blood leaving solid waste
   • Stomach
     • stores food and mixes it with digestive juices
     • makes acid to kill bacteria
   • Pancreas
     • produces more digestive enzymes

2. Nutrition

   • Ingestion
     • taking food into the mouth
   • Digestion
     • breaking down of food into its molecules
     • physical/chemical
   • Absorption
     • passing of the food molecules through the walls of the small intestine and into the bloodstream
   • Assimilation
     • body cells take in the food molecules from the blood
       • cells use food molecules for energy, growth and repair
   • Egestion
     • undigested food is passed out of the body
       • e.g. Fibre

3. Digestion

   • Chemical
     • second stage of digestion
     • enzymes
       • made in mouth, stomach, pancreas and small intestine
       • catalysts
     • An Enzyme is a chemical, made in a living cell, which can speed up a chemical reaction, without itself being changed
     • substrate
       • substance enzyme acts on
     • product
       • broken down substrate
   • Phyical
     • first stage of digestion
     • breaking down of food into smaller pieces in the mouth
     • teeth
       • [Image: http://www.gtchild.co.uk/content/images/stories/human_body/teeth_mouth.jpg]
       • incisors
         • sharp teeth at front of mouth
         • used to cut food
       • canines
         • pointed teeth which tear food
       • premolars
         • flat teeth used to grind food
       • molars
         • large, flat teeth at the back
         • also used for grinding

4. An Enzyme in Action

   • Starch
     • carbohydrate made up of long chains of glucose molecules linked together
     • broken down in the mouth and small intestine by an enzyme called amylase
   • Amylase
     • breaks down starch into many molecules of a sugar called maltose
     • enzyme
   • Maltase
     • enzyme
     • acts on maltose molecules breaking them down into single glucose molecules
   • glucose molecules
     • final breakdown products of starch
     • small enough to be absorbed into blood
       • through wall of small intestine