Objectives
• Identify
the parts of the digestive system
• Outline
the role of the stomach and the small intestine in breaking down food
• Discuss
the difference in pH of the stomach and the small intestine
Role of the stomach
• Storage
of food
• Conversion
of food by gastric juice into a soft semi-fluid mass which is released into the
duodenum for transfer to the small intestine
• Protein
digestion. Gastric juice contains
enzymes which start breaking down proteins.
Hydrochloric acid keeps the stomach at the best pH for these enzymes.
• Not
much food is absorbed into the body in the stomach
• A
small amount of water is absorbed
• Some
fat-soluble substances are absorbed
Role of the small intestine
• Completing
the breakdown of food using:
– Digestive
juices from the pancreas
– Bile
form the liver (emulsify fats)
– Enzymes
from the wall of the intestine (proteins converted to amino acids)
– Carbohydrates
converted to glucose
• Most
water is digested in the duodenum and small intestine
pH in the digestive system
• HCl
makes the stomach much more acidic than the small intestine
• Pancreatic
juice is alkaline. This neutralises the
HCl and generates the ideal pH for the enzymes in the small intestine
Review of Objectives
• Identify
the parts of the digestive system
• Outline
the role of the stomach and the small intestine in breaking down food
• Discuss
the difference in pH of the stomach and the small intestine
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