* mechanical digestion * intital digestion of proteins and lipids
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small intestine functions
chemical and mechanical digestion
absorption
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large intestine functions
* compaction of feces * absorption * defecation
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What is ingestion?
taking food and drinks into oral cavity
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what is digestion?
* breaking down foods into usable forms
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What is the difference between chemical and mechanical digestion?
* chemical: use of enzymes to break down polymers into monomers for absorption * mechanical: alters consistency of food to ease transport
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What is the movement of materials into digestive tract epithelium → interstitial fluid→ blood/lymph?
absorption
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What is compaction?
absorbing all usable material and consolidating the ingestible and nonabsorbable materials as feces
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What is the function of protection of the digestive system( (epithelium and lymphoid tissue)
* epithelia protect against abrasion, chemical damage, pathogens * lymphoid tissue protects against pathogens that enter interstitial fluid * stomach acid
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What structures are included in the digestive tract (alimentary canal)?
mouth, esophagus, stomach, small intestine, large intestine
acute inflammation of the peritoneum caused my infection microbes, GI tract rupture, perforated ulcer, trauma, appendicitis
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which cranial nerve controls the tongue?
CN XII (hypoglossal)
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What is the function of the tongue?
* mechanically break up food * manipulate food into a bolus * glands secrete saliva and ligual lipase * ducts of salivary glands open near lingual frenulum
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What are the functions of saliva?
* mucus for lubrication * enzymes that initiate the digestion of carbs and lipids * IgA antibodies and lysozyme * solvent for dissolving food molecules * bicarbonate that neutralizes bacterial acids
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What is the function of the upper esophageal sphincter?
prevents air from entering esophagus when contracted
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How many layers of muscularis externa is in the stomach? what is the function of the extra layer?
* 3 * prevents over-stretching and helps churn food
* stem cells that replace lost pit and gland cells
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G cells
secrete gastrin
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Parietal cells generate __ from __ , then pump into lumen while exchanging __.
* H+ * carbonic acid * K+
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what is bicarbonate exchanged for in gastric hydrochoric acid?
* plasma chloride ions
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CO2 is converted to carbonic acid, carbonic acid dissociates into _____ ,__ __*, ,*__ *then* __*, _*__ *moves in and __moves out.*
* K+, H+, HCO3- * chloride moves in * bicarbonate moves out
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What pump facilitates the gastric hydrochloric acid formula
protein H+ K+ ATPase pump
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What is the function of gastric hydrochloric acid
* kills microbes, denatures food enzymes, breaks down plant cell walls, meat CTs * activates pepsinogen and lingual lipase
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Where does the initial digestion of lipids take place, and by what?
in the mouth/stomach by lingual lipase and gastric lipase
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How is pepsin autocatalytic?
catalyzes own reaction by splitting amino acids to activate pepsinogen, that activates more pepsin
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why is there little absorption in the stomach?
* thick mucus * lack of transport proteins * tight junctions
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Mucus cells contain ___________ which converts ethanol to acetaldehyde
alcohol dehydrogenase
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Function of duodenum
* recieves chyme from stomach and secretions from accessory organs * neutralizes stomach acid * inactivates pepsin * emulsifies lipids * site of pancreatic enzyme function
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Jejunum function
* majority of chemical digestion and absorption occur here
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Ileum function
* lymphoid nodules protect against bacteria
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Small intestine villi
* absorb nutrients and deliver to liver * each contains a lacteal
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What is a lacteal?
* lymphatic capillary that absorbs lipids
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small intestine microvilli
* form brush border enzymes (BBEs) * increase surface area for absorption
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BBE functions
* carry out final stage of digestion * peptidases and enteropeptidase
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Small intestine - intestinal crypts
* what does upper portion contain? * what does lower portion contain? * what cell secretes lysozyme?