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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
What part fo the CNS regulates the release of saliva into the oral cavity?
What is the function of the esophagus?
- muscular tube that expands to allow bolus to pass
- adds mucous to food
- passageway to stomach
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
What mechanical factors are involved in digestion in the stomach?
pacemaker cells in muscularis
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
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
Explain how both negative and positive feedback mechanisms are part of stomach activity.
- Negative: SNS, CCK, secretin
- Positive: PNS, gastrin
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
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
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
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
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
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
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
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
Give examples of how the liver functions in each of the following ways:
- 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
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