the stomach cardiac sphincter. walls of the digestive tract the digestive tract wall has four...
TRANSCRIPT
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The Stomach
Cardiac Sphincter
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Walls of the Digestive Tract
The digestive tract wall has four layers: Mucosa: mucous membrane – secretes digestive
enzymes and mucus – inner most layerSubmucosa: loose connective tissue – houses blood
and lymph vesselsMuscularis: two layers of smooth muscle - for
peristalsisSerosa: serous membrane – secretes serous fluid to
prevent sticking – outermost layer
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Muscularis
Mucosa
Submucosa
Serosa
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Entering the Stomach
Stores food/liquid (up to 2L!) and aids in digestion Term gastric always refers to the stomachThe wall of the stomach is protected by a thick layer
of mucusFood from the esophagus passes through the
cardiac sphincter into the stomachMuscular stomach wall churns (mechanical
digestion) the bolus(food), mixing the food with gastric juice (chemical digestion)
Alcohol is absorbed but not food
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Stomach
Thick walled J-shaped organ lies on the left side of the body beneath the diagram
Mechanical Digestion/Processes1.Crushing2.Churning3.Moistening4.Absorption of liquids5.Absorption of simple sugars
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Stomach Digestion
Stomach mucosa has millions of gastric pits which lead into gastric glands Gastric glands produce Gastric Juice
Gastric Juice contains: Hydrochloric acid (HCl) Pepsin (active form of enzyme)
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Gastric Juice
Hydrochloric acid (HCl)Kills most bacteria present in foodDoes not digest food but breaks down the
connective tissue of meatActivates Pepsinogen to form PepsinPepsinogen Pepsin
Inactive enzyme HCl active enzymeCreates pH of 2 in the stomach
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Gastric Juice
Pepsin (active form of enzyme) From Pepsinogen (inactive enzyme) Is a protease - digests proteins Digests protein in the bolus into smaller
polypeptidesProtein shorter polypeptide
PepsinOptimal pH of Pepsin: 2-3
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Stomach Video
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter26/animation__organs_of_digestion.html
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Questions
What does a pH of 2 indicate? Acidic - corrosive
What protects our stomach from this corrosive environment? A thick layer of mucus is present on the stomach walls
What would happen if HCl penetrated the mucus wall? The HCl would start to corrode the stomach wall creating an
ulcerMost ulcers are due to a bacterial infection which
impairs the cells to produce the protective mucus
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Lab Activity
Work in partnersMust wear gogglesCleanup:
Empty beakers into the designated containers Ensure your area is clean – no paper towels or
liquidsIf you finish early start on the discussion questions
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Lab Discussion
1. What is a simulation?
2. What is the purpose of creating a digestive system simulation? Can you think of any examples?
Biomedical engineers have created the world’s first artificial stomach
Mimics many activities that take place in your body and can even throw up.
Allows scientists, doctors, and pharmacists to know what happens to our food or medicine after we swallow it
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Lab Discussion
3. The two tablets you tested today were medication that is commonly used to relieve pain or fever – aspirin. What were the differences between the two tablets?
Why do you think there are these differences?
4. Why might it be a good idea to test new medicines in a simulated environment rather than on a real person?