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6 processes of the digestive system
- ingestion
- secretion - (enzymes, acids, water, etc)
- mixing and propulsion - contract and relax to turn food into nutrient molecules
- digestion
- absorption
- elimination/defecation
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types of digestion
- mechanical - teeth grind food, enzymes disolving molecules
- chemical - splitting of large (carb, lipid, protein, nucleic acid)
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divisions of digestive system
- the alimentary canal (digestive tract)
- accessory digestive organs
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histology of alimentary canal
- mucosa - inner lining og GI tract, secrete hormones, mucus, absorbs end products, protects against infection
- submucosa - contains lymphoid molecules, potect aginst disease, blood vessels, and elastic tissue
- muscularis - contains smooth and skeletal muscle (segmentation and peristalsis)
- serosa - not found in esphagus
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5 major peritoneal folds and ligaments
- greater omentum - largest peritoneal fold. also has a lot of adipose tissue, lympth nodes
- falciform ligament - attaches to liver and anterior abdominal wall and diaphragm
- lesser omentum - pathway for blood vessels entering the liver, and contains the hepatic portal, artery, bile duct, and lymph nodes
- mesentery - a fan shaped fold of the peritoneum, loaded with fat
- mesocolon - two seperate folds of the peritoneum, carries blood to lympathic vessels to the intestines
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bolus
food ground into bolus (in mouth)
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what begins chemical breakdown of food
salivary gland
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types of salivary glands
- submandibular glands (found underneath the mandible)
- sublingual glands (underneath the tongue)
- parotid glands (between ear and masseter and skin)
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enamel
hardest surface in the body
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esophogeal glands produce
mucus, to lubricate bolus and reduce friction
** peristalsis begins in the esophagus
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esophageal process
- peristalsis
- esophagus does not produce digestive enzymes
- oesophagus does not carry the absorption
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chyme
bolus + gastric gland secretion
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protein digestion
begins in the stomach
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goblet cells
secret mucus
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parietal cells
secrete hydrochloric acid (pepsinogen to pepsin) and intrinsic factor (absorption of B12)
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chief cells
secrete pepsinogen and secrete gastric lipase
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enteroendocrine cells
release hormones (histamine, serotonin, gastrin, endorphins, somatostatin)
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gastric phase
- stomach distension activates stretch receptors
- food chemicals activate chemoreceptors which activate G cells which secrete gastrin
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90% of digestion and absorption
occurs in small intestines (duodenum, jujunum, ileum, plicae circulares)
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villa
increase surface area for absorption and digestion
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microvilli
also increase surface area
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functions of the pancreas
- islets of Langerhans release insulin and glucagon, remaining 1% of clusters form the endocrine
- pancreatic exocrine cells secrete pancreatic juice
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functions of large intestines
- reabsorption of water/electrolytes
- production and absorption of vitamin B and K
- elimination of feces
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goblet cells produces
mucus for lubrication of feces
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IBS
affects large intestines
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peritonitis
inflamed infected pouches ruptures, spilling intestinal contents into abdominal cavity
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crohns disease
mostly affects ileum and the cecum
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