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Mechanical and Chemical Digestion. Grade 8 Semester 1 Year 2011-2012. How Important is Your Teeth?. What happen inside our mouth?. Mechanical digestion Food is cut up by the teeth and the pieces are mixed with the saliva by the tongue producing bolus.

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Mechanical and Chemical Digestion

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mechanical and chemical digestion

Mechanical and Chemical Digestion

Grade 8 Semester 1

Year 2011-2012

what happen inside our mouth
What happen inside our mouth?
  • Mechanical digestion
  • Food is cut up by the teeth and the pieces are mixed with the saliva by the tongue producing bolus.
  • This cutting and mixing is called mastication (chewing)
types of tooth
Types of Tooth
  • Adults humans typically have 32 teeth
  • Humans have 4 types of teeth:

Incisors-cutting and biting

Canine-holding and cutting

Premolars-chewing and crushing

Molars-chewing and crushing

tooth structure
Tooth Structure

Enamel: hardest tissue made of calcium salts.

Dentine: forms the major part of the tooth. Contains a series of fine canals which extend to the pulp cavity.

Pulp cavity: Contains tooth producing cells, blood vessels, nerve endings.

Gum: Covers the junction between enamel and cement.

Cement: helps anchor the tooth to the jaw.

Periodontal membrane: Anchors the cement to jawbone. The tooth is held firmly but not rigidly.

dental health
Dental Health
  • Eating food with a low sugar content.
  • Regular and effective brushing of teeth (at least twice a day).
  • Finishing a meal with a crisp vegetable or fruit followed by rinsing with water.
chemical digestion1
Chemical Digestion

Digestive Enzymes

  • Carbohydrate digestion begins in the mouth.
  • Protein digestion begins in the stomach.
  • Digestion of food molecules is completed in the small intestine.
  • Absorption is a process where digested food molecules are transported across the lining of the gut into the blood.
  • Most absorption happens from the ileum.
  • The surface of the ileum is highly folded into villi.
structure of small intestine

Microvilli(brush border)

Vein carrying blood to hepatic portal vessel


Muscle layers


Epithelial cells








Intestinal wall

the liver and assimilation
The liver and assimilation
  • Digested food is absorbed into the bloodstream.
  • The liver sorts out digested food molecules and make sure that the other tissues of the body receive what they need.
  • The process of moving food molecules into the cells where they are used is called assimilation.
functions of liver





Acid chyme



Pancreatic juice

Duodenum of small intestine

Functions of Liver
  • Manufacture of bile
  • Storage of glucose as glycogen
  • Interconversion of amino acids
  • Excretion of excess amino acids and excreted in the urine as urea
  • Breakdown of alcohol and other toxins
  • Removal of old red blood cells from the circulation and storage of the iron they contained

Bread is made mainly of starch, protein and fat. Describe what happens to the bread mechanically and chemically as it passes through the mouth, stomach and small intestine.