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The Digestive System. Digestion is the process of breaking down food into molecules the body can use. How is food digested?. Digestion involves: Breaking down of food into smaller pieces The mixing of food Movement through the digestive tract

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the digestive system

The Digestive System

Digestion is the process of breaking down food into molecules the body can use

how is food digested
How is food digested?

Digestion involves:

  • Breaking down of food into smaller pieces
  • The mixing of food
  • Movement through the digestive tract
  • Chemical breakdown of the large molecules of food into smaller molecules.
two types of digestion
Two Types of Digestion
  • Mechanical – physically changing the size of food
    • Ex: grinding action of teeth
    • Ex: churning action of stomach
  • Chemical – a change in the chemical nature of the nutrients
    • Ex: amylase (in saliva) working on starch
gastrointestinal tract
Gastrointestinal Tract
  • a series of hollow organs that food passes through
  • Also known as the alimentary canal
    • Alimentary: of or relating to nourishment or nutrition
mouth oral cavity
Mouth (oral cavity)


-mechanical digestion

  • Chemical Digestion:
    • Amylase Enzymes in saliva chemically digest carbohydrates.
mouth oral cavity1
Mouth (oral cavity)


  • Keeps food in place
  • Push bolus to back of mouth
    • Bolus: a soft mass of chewed food
more to the mouth

Dangling“thing” in back of throat

Catches bacteria and dirt particles

Can be destroyed by bulimics

More to the Mouth
Open area at back of the mouth

Passageway for both food & air

Epiglottis – thin flap that prevents food from entering the trachea


Tube about 25cm long

connects the pharynx to the stomach.

2 layers of muscle.


  • peristalsis
    • Wavelike, involuntary muscle contractions that pushes food through the digestive tract

Both mechanical and chemical digestion

Mechanical Digestion

3 layers of muscle that twist and turn the stomach

Results in churning action = mechanical

Makes your stomach “growl”

  • Chemical digestion:
    • Stomach lining produces HCl (hydrochloric acid) to breakdown and dissolve nutrients
    • Enzyme – Pepsin begins to digest proteins
    • Bolus becomes Chyme

small intestine
Small Intestine
  • 7 meters long (22feet)
  • Site of nutrient diffusion into blood from mesentary

small intestine1
Small Intestine
  • Mesentary:
    • Contains blood vessels

that Absorb the nutrients

large intestine
Large Intestine
  • Water and Minerals (NaCl) are absorbed back into the blood
  • The remains are formed into brown, semi-solid feces
large intestine1
Large Intestine
  • Diarriaha
    • Water was not reabsorbed
  • Constipation
    • Too much water was reabsorbed
rectum and anus
Rectum and Anus
  • Rectum = store the feces.
  • Anus: ring of muscle that squeezes the feces out of the body.
accessory organs
Accessory Organs
  • Aid (help with) in digestion but food never travels through
  • Liver, Pancreas, Gall bladder
  • The liver is like a processing factory with more than 200 different jobs.
    • Produces bile
      • Bile: breaks down fats in the small intestine.
    • Stores some nutrients
      • brought from the blood after the small intestine
    • Produces cholesterol
    • Detoxifies
  • Produce insulin and enzymes
  • Enzymatic juices travel through the common bile duct into the small intestine

gall bladder
Gall Bladder
  • A small baglike sac under the liver.
  • It stores bile.
  • Empties the bile into the small intestine via the common bile duct
common bile duct
Common Bile Duct
  • Collects from liver, gallbladder, pancreas and empties into the small intestine
to quiz yourself over the parts of the digestive system click here

To quiz yourself over the parts of the digestive system, click here:

describe water
Describe water
  • Most of the nutrients in your body can't be used unless they are carried in a solution. This means that they have to be dissolved in water.
  • In cells, chemical reactions take place in solutions.
describe water1
Describe water
  • Most of the material absorbed from the cavity of the small intestine is water in which salt is dissolved.
  • The salt and water come from the food and liquid we swallow and the juices secreted by the many digestive glands.
for more information about the digestive system click here

For more information about the digestive system, click here: