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What is the primary function of the digestive system?
To bring essential nutrients into the body
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What 7 mechanisms are used to accomplish the primary function of the digestive system?
Ingestion, Digestion, Motility of GI wall, secretion of enzymes, Absorption, Elimination, Regulation
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What is ingestion?
The process of taking food into the body
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What is digestion?
The breakdown of nutrients
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What is the function of the motility of the GI wall?
physically breaks down large chunks of food and moves food along tract
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What does digestive enzymes do?
Allow chemical digestion
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What is absorption?
movement of nutrients through the GI mucosa
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What is elimination?
Excretion of material not absorbed
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What is regulation?
coordination of various functions of the digestive system
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The digestive tract is functionally an...
extension of the external environment; not truly part of internal environment until absorbed
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How many microbes are throughout the digestive system?
Thousands
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What is mechanical digestion?
movements of the digestive tract
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What is mastication?
process of chewing food
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What is the first part of mechanical digestion?
To change large food particles into minute particles, facilitating chemical digestion
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What is the 2nd step in mechanical digestion?
To churn contents of the GI lumen with the surface of the intestinal mucosa, facilitationg absorption
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What is the 3rd part of mechanical digestion?
To propel food along the alimentary tract for elimination
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What is Deglutition?
the process of swallowing
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How many stages of deglutiition are there?
3
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What is the first step of deglutition?
- The oral stage (mouth to oropharynx):
- VOLUNTARY
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What is the 2nd step of deglutition?
- Pharyngeal stage (oropharynx to esophagus):
- INVOLUNTARY MOVEMENT
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What is Peristalsis and segmentation?
2 main types of motility produced by the smooth muscles of the GI tract.
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What is peristalsis?
wavelike ripple
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What is segmentation?
Mixing movement
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What is gastric motility?
emptying the stomach takes approx. 2-6 hours. Food is churned and mixed with gastric juices to form chyme
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What does chyme pass through?
pyloric sphincter
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After leaving the stomach, how long does it normally take chyme to pass thru the small intestines?
approx 5 hours
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Absorption occurs thru...
villae and microvillae in small intestines
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What is chemical digestion?
Changes in chemical composition of food as it travels thru the digestive tract.
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What kind of digestion results in hydrolysis?
Chemical digestion
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Chemical digestion enzymes function optimally...
at a specific pH
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What happens to sugars when they aren't broken down?
They ferment
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Carbs are ....
saccharide compounds
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Protease break down proteins into...
amino acids
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What are amino acids?
building blocks of proteins, cell membranes and etc
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What does fat digestion entail?
Fats must be broken down by bile in small intestine before being digested
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What is the main fat-digesting enzyme?
Pancreatic lipase
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What 2 things are the result of fat break down?
glycerol and ketone bodies
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What has to be coded in order to be digested?
Fats
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Salivary glands secrete...
saliva
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What enzyme begins digestion of starches?
Amylase
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What increases the pH for optimal amylase function?
Sodium Bicarbonate
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What is secreted by parietal cells?
Hydrochloric acid
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What is secreted by gastric glands?
Gastric juices
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What actively releases hydrochloric acid into gastric juices?
Hydrogen- potassium pumps
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What is another name for hydrogen pumps?
Proton pumps
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HCl is one of the primary acids in...
stomach
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Prilosec is considered a ...
proton- pump inhibitor because it turns off the pumps that produce gastric acid
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What secretes the intrinsic factor?
parietal cells
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What does the intrinsic factor do?
protects vitamin B12 and later facilitates absorption
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What must happen for B12 to pass into the blood stream?
It has to be paired with an intrinsic factor
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What secretes pancreatic juice?
acinar and duct cells of the pancreas
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What are proteases?
enzymes that digest proteins and polypeptides
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Which enzymes digest emulsified (broken down) fats?
Lipases
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Which enzymes digest nucleic acids such as DNA and RNA?
Nucleases
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Where is bile secreted and then stored?
secreted in the liver and stored and concentrated in gallbladder
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What is secreted by the intestinal exocrine cells?
Intestinal juice
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Olfactory and visual stimuli come from...
the smell and sight of food
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Gastric secretion has how many phases?
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Pancreatic secretion is stimulated by...
several hormones released by intestinal mucosa
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Most absorption occurs in...
the small intestine
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What is gastric bypass?
bypassing the small intestine which prevents food from being absorped
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For absorption to happen, food has to be...
absorbed thru the cell wall of the duodenum
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What is elimination?
the expulsion of feces from the digestive tract
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What is defecation?
the act of expelling feces
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What is constipation?
contents of lower part of colon and rectum move at a slower than normal rate
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What is diarrhea?
result of increased motility of the small intestine, causing decreased absorption of water and electrolytes and a watery stool
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The colon only absorbs...
Water
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Oxygen for digestive activity depends on...
proper functioning of the resp and circulatory systems.
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