Human Digestive System

Human Digestive System

1. General Terms

   • Digestion
     • The physical and chemical process by which food is broken down into smaller, soluble molecules that can be absorbed into the bloodstream
       • Physical digestion
         • The mechanical action of teeth, jaw and muscle movement
           • Mouth
             • Mastication
               • Chewing using teeth and jaw movement
           • Muscle
             • Peristalsis
               • Oesophagus
               • Small intestine
             • Contractions in stomach wall
           • Other
             • Small intestine
               • Bile emulsifying fat
         • Breakdown of large food molecules into smaller molecules
           • Increases surface area
             • Increases efficiency of chemical digestion
       • Chemical digestion
         • Action of enzymes and gastric juices
           • Mouth
             • Amylase enzyme
           • Stomach
             • Gastric fluids
           • Small intestine
             • Pancreatic juice
   • Enzymes
     • Complex proteins folded into specific shapes
       • Have an active site
         • Only fits a specific substrate
     • Helps break down large food molecules into smaller, soluble molecules that can be absorbed into the bloodstream by catalysing chemical reactions in the digestive system

2. Mouth

3. Stomach

   • Lined with gastric pits
     • Produces gastric fluids
       • Hydrochloric acid (HCl)
         • Acidic (pH 1-2)
       • Mucus
         • Protects stomach lining from corrosive nature of the HCl
       • Pepsin
         • A protease
           • Catalyses the breakdown of proteins into polypeptides
             • Liquifies the food into chyme
               • Semi digested food
   • Large, elastic walls
     • Can hold 2-4 L of food
       • Meal can be ingested quickly and digested slowly
     • Muscular contractions of stomach walls
       • Churns food
       • Thoroughly incorporates food with gastric fluids

4. Small Intestine

5. Large Intestine