The Digestive System

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The Digestive System
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Why do we EAT?

• To obtain ENERGY
• Cells convert food energy into ATP
• Calories
• How much energy food has
• When food is burned, it is converted into heat

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The ALIMENTARY Canal

• One-way tube through the body
• Major structures
• Mouth
• Pharynx
• Esophagus
• Stomach
• Pyloric Sphincter
• Mesentery
• Small intestine
• Duodenum
• Large intestine
• Caecum
• Accessory structures
• Salivary glands
• Pancreas
• Liver

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Digestion - The Mouth

• Digestion begins at the mouth
• Mechanical digestion teeth, chewing
• Chemical digestion saliva and other digestive
  enzymes
• Main goal of digestion to break down food into
  SIMPLE molecules so body cells can use them

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The Esophagus

• Connects throat to stomach
• Bolus lump of chewed food that passes down
  throat
• Smooth muscle contractions move bolus along to
  the stomach

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The Stomach

• Stomach continues mechanical and chemical
  digestion
• Contains many enzymes
• Mixture of food and enzymes travels to small
  intestine
• Pyloric sphincter
• Pinched in section that separates stomach and
  small intestine

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The Small Intestine

• Duodenum- top 1/3 of small intestine
• Most food absorption happens here!
• Contains villi (tiny projections) that increase
  surface area

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The Large Intestine

• Removes water from any undigested material
• Bacteria here help body make Vitamin K

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Accessory Organs

• Pancreas
• Regulates blood sugar levels
• Makes digestive enzymes
• Makes substance that neutralizes stomach acid
• Liver
• Makes bile which digests fats

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Disorders of the Digestive System

• Ulcers
• Caused by Helicobacter pylori treated with
  antibiotics
• Diarrhea
• Not enough water absorbed by large intestine
• Constipation
• Too much water absorbed by large intestine