the digestive system lab. organs of the digestive system gastrointestinal tract (git) –...
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The Digestive SystemThe Digestive SystemLabLab
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Organs of the Digestive System Gastrointestinal tract (GIT) – continuous passageway which contains the food from the time it enters the body until it leaves; organs include:
mouth (oral cavity), pharynx (oropharynx & laryngopharynx), esophagus, stomach, small intestine (duodenum, jejunum, ileum), large intestine (cecum, colon, rectum), anal canal, anus
Accessory organs - participate in digestive processes; organs include:
teeth, tongue, salivary glands, liver, gall bladder, pancreas
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Function of the Digestive System
To break down food into a “usable” (absorbable) form – occurs through mechanical processing & chemical digestion
To supply our cells with the nutrients they need for energy, growth & repair
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carbohydrates – including
polysaccharides (“complex” carbohydrates )
starch
disaccharides (“simple” sugars)
maltose, sucrose, lactose
proteins
fats (lipids/triglycerides)
vitamins
minerals
water
Classes of Nutrients:
No digestive processes necessary, just absorption
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Digestive processes
Mechanical processing – physical breakdown of food; e.g. mastication, emulsification, mixing waves, segmentation
Chemical digestion – chemical breakdown of food; disassembling of organic molecules into their component parts; requires enzymes
carbohydrates (polysaccharides) disaccharides monosaccharides
proteins amino acids lipids (triglycerides) fatty acids & glycerol (monoglycerides)
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Mouth (oral cavity)
Parotid gland
Submandibular gland
Sublingual gland
saliva – made of H2O, salts & salivary amylase; moistens foods to create “bolus” to help with deglutition, & begins chemical digestion of starch
Digestion (mechanical & chemical) begins within the oral cavity –
mastication
production of saliva by salivary glands
Starch (polysaccharide) Maltose (disaccharide)amylase
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StomachMechanical digestion – mixing waves to change bolus of food to “chyme”
Chemical digestion - secretions from cells of stomach to begin protein digestion: Peptic (chief) cells – pepsinogen
Parietal cells – hydrochloric acid (HCL)
Pepsinogen + HCL Pepsin
Proteins Pepsin
HCL
polypeptides
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Small intestineChyme from stomach (with partially digested starch & proteins) + Bile from liver & gall bladder + Pancreatic juice from pancreas – released into duodenum of small intestine
Segmentation mixes chyme with other secretions
Fats + bile emulsified fats
bile
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Stomach
HeadBody
Tail
PancreasPancreatic juice – mixture of enzymes & buffers (sodium bicarbonate) secreted by acinar cells into pancreatic duct & released into duodenum
lipase
Lipids (triglycerides) fatty acids + monoglycerol proteases (trypsin, chymotrypsin, carboxypeptidase)
Proteins & polypeptides small peptides (tripeptides & dipeptides)
nucleases – digest RNA & DNA
sodium bicarbonate – neutralizes acidic chyme because enzymes in small intestine need an alkaline pH
pancreatic amylaseStarch maltose
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Small intestineCells in jejunum and ileum produce peptidases and disaccharidases for final digestion of proteins and sugars
small polypeptides, tripeptides, dipeptides
peptidases amino acids
maltosemaltase
glucose + glucose
sucrosesucrase
glucose + fructose
lactoselactase
glucose + galactose
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Absorption
Absorption of monosaccharides (glucose, fructose, galactose), amino acids and fatty acids (as well as vitamins/minerals) occurs in small intestine (into blood or lymph (fatty acids)Absorption of water (and some vitamins) occurs in large intestine