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What are the primary mechanisms of the digestive system?
- ingestion
- digestion
- motility
- secretion
- absorption
- elimination
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What is the condition of digestive activity called?
regulation
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What are the three steps or stages of deglutition?
- oral stage (mouth to oropharynx), voluntary movement
- pharyngeal stage (oropharynx to esophagus)
- esophageal stage (esophagus to stomach)
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What is progressive kind of motility that is a type of motion that produces forward movement of ingested material along the GI tract; it is a wavelike ripple of muscle layer?
peristalsis
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What can be described as mixing movement, when digestive reflexes cause a forward-and-backward movement withinn a single region, or segment, of the GI tract?
segmentation
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The process of emptying the stomach takes about how mnay hours?
2 to 6 hours
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What is known as when food is churned with gastric juices to form a thick, milky material?
chyme
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Chime is ejected about every how many seconds into what?
every 20 seconds into the duodenum
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What hormone is released when fats and other nutrients in the duodenum stimulate in the intestinal mucosa?
gastric inhibitory peptide (GIP)
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The chemical process in which a compound unites with water and then splits into simpler compounds is called.
hydrolysis
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What enzymes are proteases (protein-digesting enzymes)?
pepsin and trypsin
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Why are digestive enzymes classified as extracellular?
they operate in the lumen of the digestive tract, outside any cells of the body
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What is the main enzyme in saliva?
amylase
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Most digestive enzymes are synthesized and secreted as what?
inactive proenzymes
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What are substances that convert proenzymes to active enzymes?
kinases
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What are polysaccharides?
starches and glycogen
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What are disaccharides?
sucrose, lactose, and maltose
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What are monosaccharides?
glucose, fructose, and galactose
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What hydrolyzes polysaccharides into disaccharides?
amylase in saliva and pancreatic juice
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What enzymes hydrolyze proteins to proteoses and peptides?
gastric juice protease (pepsin) and pancreatic juic protease (trypsin and chymotrypsin)
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When is protein digestion completed?
pancreatic proteases (trypsin and chymotrypsin), which hydrolyze proteoses to amino acids,, and by intestinal peptidases, which hydrolyze peptides to amino acids
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What enzymes are catalyzing at the final steps in carbohydrate digestion?
sucrose, lactase, and maltase
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What are two substances found in bile?
lecithin and bile salts
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Lecithin mixes with lipids and water forming tiny spheres called?
micelles
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What is the mechanical process of emulsification?
facilitates chemical digestion of fats by breaking large fat drops into small droplets
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What are the main fat-digesting enzymes called?
amylase
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What binds to hydrogen ions, thus taking the hydrogen ions out of solution and causing a decrease in acidity (increase in pH)?
sodium bicarbonate (small amount found in saliva)
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What type of juice is secreted by exocrine gastric glands, which have ducts that lead to the gastric lumen by way of the gastric pts?
gastric juice
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What is secreted as the exocrine acinar cells?
pancreatic juice
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What is secreted as tthe inactive proenzyme pepsinogen?
pepsin (pepsinogen is converted to pepsin by hydrochloric acid)
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What is an interesting mixture of many different substances that is secreted by the liver, stored, and concentrated by the gallbladder?
bile
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What is referred to the sum of interstinal secretions rather than to a premixed combination of substances, that enters the GI lumen by way of a duct?
intestinal juice
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What the 3 types of phases in the control of gastric secretion?
- a) cephalic phase-"psyhic phase," psychic factors activate the mechanism
- b) gastric phase-gastrin is released by the stimulation of the mucosa
- c) intestinal phase-endocrine reflexes involving gastric inhibitory peptide, secretin and CCK inhibit gastric secretions
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What hormones are secreted by endocrine cells in the mucosa of the duodenum?
gastric inhibitory peptide (GIP), secretin, CCK
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What hormone evokes the producitn of pancreatic fluid flow in enzyme content buy high in bicarbonate (HCO3)?
secretin
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What intestinal hormone stimulates contraction of the gallbladder so that bile can passs into the duodenum?
cholecystokinin (CCK)
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What is the passage of substances through the intestinal mucosa into the blood or lymph?
absorption (most absorption occurs in the small intestine)
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What is the final step in lipid transport by the intestine?
formation of chylomicrons
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Where is chylomicrons formed by?
the golgi apparatus
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