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What is the function of saliva?
- moisten and dissolve food to form bolus
- add enzymes that kill nora flora
- contains IgA that can inhibit bacterial growth
- min. influence on starch digestion
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What part fo the CNS regulates the release of saliva into the oral cavity?
parasympathetic
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What is the function of the esophagus?
- muscular tube that expands to allow bolus to pass
- adds mucous to food
- passageway to stomach
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What is the relationship b/w heartburn and the cardiac sphincter?
if the stomach churns and the cardiac sphincter is not closed completely stomach acid will go up the esphagus causing heartburn
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What mechanical factors are involved in digestion in the stomach?
pacemaker cells in muscularis
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What chemical factors are involved in digestion in the stomach?
- pepsinogen: secreted by chief cells
- HCl: made by parietal cells
- if amylase isn't altered, starch break down continues here too
- gastric lipase begins fat break down
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Describe the hormonal and neural regulation of activities in the stomach.
- stretching of smooth muscle in walls which food enters and sensory input sends message to parasympathetic
- para is responsible of the release of gastrin: increaes release of HCl and pepsinogen, increase peristalsis, shuts the cardiac sphincter, relax the pyloric spincter
- stimulated the release of histamine from other enteroendrocrine cells which encourages the release of HCl
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Explain how both negative and positive feedback mechanisms are part of stomach activity.
- Negative: SNS, CCK, secretin
- Positive: PNS, gastrin
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Describe the mechanisms used in the absorption of carbs
- glucose is moved into cells by Na+ co-transport
- also moved b/w cells by solvent drag
- others monosaccharides moved in by different proteins
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Describe the mechanisms used in the absorption of proteins
- slowly broken down into individual amino acids that are moved into brush boreder cells
- Na+ co-transport and facilitated diffusion
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Describe the mechanisms used in the absorption of minerals
- combination of co-transport, simple diffusion and active transport
- most absorbed entire SI in a non-selective manner
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Describe the use of micelles to move fat into the brush border of the SI
- bile (lecithin and cholesterol) form tiny micells
- lipase breaks up tryiglyceride chains
- micelles bind to various lipids
- eventually moved into brush border
- micelles stay in SI and bind to more lipids
- majority of lipids pass into lymphatic vessels and eventually to blood stream
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List functions of CCK
- arrival of fats and acids trigger release
- Target organs: GB to release bile, pancreas to release enzymes, inhibit action of the stomach and keep pyloric sphincter shut
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List functions of secretin
- arrival of acidic chyme
- Target organs: liver to produce more bile, panreas to release juices, inhibit action of the stomach adn keep pyloric sphincter shut
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Compare the large intestine to the small intestine as to structure and functions.
- Large intestine: completes needed water absorption, absorbs minerals, houses normal flora; mechanical haustra- muscular pouches use food fiber to work muscles and compact food
- Small Intestine: mechanical digestion-peristalsis
- chemical digestion- zymogens form pancreas such as trypsin, pancreatic lipase, pancreatic amylase
- absorption: carbs, lipids, proteins, minerals, nucleic acids, water, vitamins
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Give the functions of the pancreas
- make digestive enzymes
- -many are inactive forms that must be activated by other enzymes in the SI
- make alkaline juices
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Give examples of how the liver functions in each of the following ways:
1. synthesis
2.storage
3.conversion
4. recycle
5. detoxification
- 1. site of gluconeogenesis, produces albumin
- 2. stores iron, glycogen, fats
- 3.deaminates proteins and handles nitrogenous waste, removes old RBC's
- 4.breaks down hemoglobin
- 5.breaks down of numerous types of compounds, including meds and drugs
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Give the composition and functions of bile
- Bile contains: bile pigment (bilirubin), bile salts (acids built from cholesterol & phospholipids & waste)
- Function: break down fats; alkenes, need to increase pH
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