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53 Cards in this Set
- Front
- Back
What is the mucosa? What are 3 major functions? What are 3 layers?
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moist epithelial layer that lines the lumen of the alimentary canal
functions: 1. secrete mucus 2. absorb end products of digestion 3. protect against infectious disease layers: 1. lining epithelium 2. lamina propria 3. muscularis mucosae |
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What are the 7 layers of the GI system, from outer to inner?
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1. serosa
2. longitudinal muscle 3. circular muscle 4. submucosa 5. mucosal muscle 6. mucosa 7. epithelial lining |
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What does the epithelia lining of the mucosa consist of?
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simple columnar epithelium and mucus-secreting goblet cells
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What is the Lamina Propria?
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loose areolar and reticular connective tissue that nourishes the epithelium and absorbs nutrients
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What is the muscularis mucosae?
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smooth muscle cells that produce local movements of mucosa
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What is the submucosa?
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dense connective tissue containing elastic fibers, blood and lymph vessels, lymph nodes, and nerves
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What is the muscularis externa responsible for?
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segmentation and peristalis
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What is the serosa replaced by in the esophagus?
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the fibrous adventitia
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What do Brunner's glands secrete?
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bicarbonate rich mucus
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What is the serosa?
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the protective viseral peritoneum
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How does the smooth muscle in the GI work as a functional syncytium?
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it has lots of gap junctions that make longitudinal movements down the muscle fast; and works as if it were a single cell.
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What do slow waves represent in terms of the electrical activity of the GI system? How many are there in the stomach, duodenum, and ileum?
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resting, NOT action potential
3 in stomach 12 in duodenum 8-9 in ileum |
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What are slow waves induced by?
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Interstitial Cells of Cajal (electrical pacemakers) within smooth muscle fibers
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What causes spikes in the electrical activity of the GI system?
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Entrance of Ca2+ through SLOW ca2+/Na+ channels
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What aspects of the GI system does the pelvic nerves innervate?
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parasympathetic: distal half of large intestine, external anal sphincter
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What are the principle effects of the myenteric/auerbach plexus? (4)
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1. increased tonic contraction
2. increaed intensity of rhythmic contractions 3. slightly increased rate of rhythmic contractions 4. increased movement of peristaltic waves |
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What are the principle effects of the submucosal/meissner plexus? (3)
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1. control of local intestinal secretion
2. control of local absorption 3. local contraction of the submucosal muscle (infolding) |
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What are short GI reflexes mediated by?
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local enteric plexuses
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What are long GI reflexes mediated by?
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involves CNS centers and extrinsic autonomic nerves
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Why does gastrin bind to cholecystokinin B receptors?
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to stimulate the release of histamines in enterochromaffin-like cells
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What does Gastrin do? What is it released by?
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stimulates secretion of HCl; released by G cells in stomach duodenum, and pancreas, induces the insertion of K+/H+ ATPase pumps into the apical membrane of parietal cells (which in turn increases H+ release)
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What does Ghrelin do? What is its counterpart
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stimulates hunger; counterpart is leptin, which is stimulated by adipose cells and induces satiation
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What does Cholecystokinin (CCK) do? Where is it made, and where is it secreted?
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stimulates the digestion of fat and protein; made and secreted in the duodenum
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What does Secretin do? Where is it produced?
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regulates pH of duodenum
produced in the Crypts of Lieberkuhn |
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What does Gastric Inhibitory Peptide (GIP) do?
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induces insulin secretion, at high levels helps to regulate pH
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What organs do the inferior and superior mesenteric arteries serve?
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small and large intestines
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What do peristaltic movements require? Why is peristaltic movement directional?
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myenteric plexus; myenteric plexis is polarized, easier to travel from mouth to rectum
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What centers in the brain is linked to chewing? (3)
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reticular formation
hypothalamus cortical taste centers |
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What is deglutition?
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swallowing
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What is GERD?
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when there isn't enough town in the lower esophageal sphincter and acids rise up into the esophagus
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What is the term for the entry of food causing dilation in the stomach?
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vasovagal reflex
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What is responsible for the export of food from the stomach?
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the pyloric pump
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What are propulsive movements like in the small intestine?
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weak, 3-5 cm
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What controls peristalisis in the small intestine
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- Gastroenteric reflex (initiated by stomach distension and transmitted through myenteric plexis)
hormones: + Gastrin, CCK, Insulin, Motilin, Serotonin - Secretin, glucagon |
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What are mixing/segmentation contractions induced by in the small intestine?
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induced by stretching
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What does the maximal frequency of mixing/segmentation contractions depend on? (2)
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electrical slow waves and the myenteric plexus
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What is the function of the ileocecal valve? What does the ileocecal valve require?
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prevents backflow from colon to ileum; there is a gastroileal reflex and also requires myenteric plexus
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What are the movements of the large intestine like?
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sluggish, modified form of peristalsis where 20 cm contract at a time
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What are mixing contractions called in the large intestine?
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haustrations (baglike protrusions)
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What secretory glands are throughout the GI mucous?
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goblet cells (cingular glands)
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What type of glands are cardiac glands?
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mucous secreting
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What do oxyntic (parietal) cells secrete?
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HCl, intrinsic factor
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What do peptic (chief) cells secrete?
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pepsinogen
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What are gastrin secreting glands sensitive to?
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pH
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What are the 3 types of tubular glands?
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cardiac, oxyntic, and pyloric
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What are the 2 types of glands in crypts?
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brunner's
lieberkuhn (large and small intestine) |
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What is intrinsic factor responsible for?
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absorption of B12
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How is HCl secreted?
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cell actively leaks Cl- and this is compensated by leaking K+ as well
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What 3 hormones control secretion of HCl?
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gastrin
histamine acetylcholine (parasympathetic) |
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How is pepsinogen converted to pepsin?
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by HCl hydrolysis
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What releases pepsinogen? What is it?
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released by chief cells in the stomach; inactive form of pepsin; protein digesting enzyme
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What is gastritis? What can it be caused by?
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inflammation of the stomach wall. due to irritants such as cigarettes, caffeine, alcohol
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What are 3 consequences of chronic gastritis?
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mucosal reduction
achlorhydia (inability to produce HCl) pernicious anemia (inability to absorb B12) |