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Digestion?
Process of breaking down foods to a form the body can use
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Absorption?
Uptake of nutrients to the blood or lymph.
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Mucosa
Innermost layer of the GI tract, lumen
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Submucosa
Second inner most layer of GI tract, has blood vessels carrying nutrients
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Muscle (GI tract)
Third layer in GI tract, moves food forward
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Serosa
Outermost layer in GI tract, protects the tract
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Lower Espoghagial Spincter
prevents backflow of stomach to espoghagus
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Pyloric spincter
controls flow of stomach acid into small intestine
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Spincter of Oddi
Controls flow of bile from common bile duct into small intestine
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Ileocecal spincter
Prevents contents in large intestine from re entering small intestine
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Anal Spincter
Prevents defecation until person chooses to
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Peristalsis
Contractions to move matter along the tract
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Saliva
Produced in the mouth, helps swallow, lubrication to mouth
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Mucus
Originates in mouth, stomach, small, large intestine. Helps protect GI tract and lubricates food.
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Enzymes ex Amylase and Lipase
Happen in mouth, stomach, small intestine, pancreas. Help digest carbs, fats and proteins.
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Acid ex HCl
introduced in the stomach, helps digest proteins and destroys microorganisms, and helps digest minerals.
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Bile
Made in liver, stored in gall bladder, digests fat.
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Bicarbonate
In the pancreas and small intestine, helps eliminate stomach acid for the small intestine
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Hormones (digestion secretions)
Stomach and small intestine, helps digest and absorb nutrients
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Saliva is composed of three things...
- lysozomes: break down bacteria
- mucus: lubricates and holds bolus together
- Amylase: breaks down starch
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Taste senses
- sour
- sweet
- bitter
- umami
- salty
- olfactory (smell)
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Gastric Inhibitory Peptide
slows release of chyme into small intestine and regulates pyloric spincter
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What do Parietal Cells secrete into stomach?
Hydrochloric Acid
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What do chief cells secrete into stomach?
Gastic lipase and pepsinogen
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What does Gastrin Do?
Hormone that controls the release of HCl and pepsinogen, releases when we think about food
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What does Mucus secrete into stomach?
Mucus protects stomach from digesting itself
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What does HCl do?
- inactivates protein
- destroys bacteria and virus
- converts pepsinogen into pepsin
- absorbs minerals
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What does pepsinogen do?
Helps digest proteins (enzyme)
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pH Scales examples
- Acids: lemon juice, vinegar, HCl, urine
- neutral: pure tears
- basic: NaOH, oven cleaner, Pancreatic juices
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What is stomach acid stimulated by?
- Gastrin, a hormone
- stomach distention
- histamine, a regulator
- thoughts of food
- food itself
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What does the liver do?
Produces bile, circulates and recycles bile
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What does gall bladder do?
Stores bile
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What does Pancreas do?
Produces bicarbonate, lipases, amylase
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What do digestive enzymes do?
- speed up chemical reactions
- each has a specific function
- controlled by hormones and nerves
- released as needed
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Order of digestion in the small intestine
- 1. enzymes secreted from pancreas
- 2. sugar break down from sacchrides to mono, microvilli brush the border
- 3. bile from the gall bladder, bicarbonate ions and enzymes from pancreas enter
- 4. segmentation mixes food with juices
- 5. 3-10 hrs later, food moves out. (95% digested)
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What are the hormones of the GI Tract?
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What are the types of absorption in the small intestine?
- Passive: fat, no energy, high to low conc, permeable wall
- Facilitated: carrier brings nutrients to cell, no energy, vitamins, high to low
- Active: ATP, energy required, glucose
- Endocytosis: phagocytosis
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What do beneficial bacteria do in large intestine?
control pathogens, synthesize vitamin K and biotin, aid in lactose digestion and fermentation
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